Change proportion of zoom in facet_zoom [ggplot2]

I would like to change the proportion of the graph covered by the "zoom". If we look at the following image we are at a ratio "graph:zoom" around 1:2 I would like instead a ratio 2:1. In other words, what I want is to reduce the height of the zoom. How should I proceed? Here is my code

require(dplyr)
require(tidyverse)
require(ggforce)
HY <- DebitH %>%
  ggplot(aes(x = Date, y = Débit_horaire)) + 
  geom_point(alpha = 6/10, size = 0.3, color = "blue") +
  geom_line(alpha = 4/10, size = 0.5, color = "blue") +
  labs(x = "Date", y = "Débit Horaire (m3/s)")+
  theme_bw() +
  theme(panel.grid.major.y = element_line(color = "grey",
                                          size = 0.25,
                                          linetype = 2),
        legend.position = "none") +
  facet_zoom(xlim = as.POSIXct(c("2021-01-15 00:00:00","2021-02-15 00:00:00")))

And here you will find a sample of the data

DebitH <-
structure(list(Date = structure(c(1610233200, 1610236800, 1610240400, 
1610244000, 1610247600, 1610251200, 1610254800, 1610258400, 1610262000, 
1610265600, 1610269200, 1610272800, 1610276400, 1610280000, 1610283600, 
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1614866400, 1614870000, 1614873600, 1614877200, 1614880800, 1614884400, 
1614888000, 1614891600, 1614895200, 1614898800), tzone = "UTC", class = c("POSIXct", 
"POSIXt")), Débit_horaire = c(5.052, 5.036, 5.009, 4.982, 4.958, 
4.937, 4.917, 4.885, 4.858, 4.834, 4.804, 4.786, 4.769, 4.753, 
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4.381, 4.352, 4.327, 4.318, 4.291, 4.27, 4.268, 4.268, 4.265, 
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4.305, 4.308, 4.32, 4.334, 4.355, 4.396, 4.457, 4.531, 4.624, 
4.738, 4.879, 5.057, 5.28, 5.558, 5.863, 6.186, 6.562, 6.958, 
7.327, 7.555, 7.638, 7.638, 7.577, 7.452, 7.291, 7.089, 6.867, 
6.646, 6.469, 6.301, 6.161, 6.043, 5.946, 5.872, 5.807, 5.752, 
5.702, 5.67, 5.658, 5.65, 5.647, 5.656, 5.692, 5.74, 5.786, 5.839, 
5.91, 6.003, 6.124, 6.256, 6.374, 6.489, 6.596, 6.686, 6.72, 
6.725, 6.706, 6.684, 6.646, 6.61, 6.578, 6.568, 6.554, 6.54, 
6.529, 6.535, 6.538, 6.542, 6.553, 6.531, 6.547, 6.54, 6.534, 
6.51, 6.504, 6.486, 6.462, 6.444, 6.429, 6.412, 6.395, 6.373, 
6.365, 6.354, 6.344, 6.334, 6.326, 6.315, 6.303, 6.295, 6.295, 
6.298, 6.296, 6.298, 6.289, 6.273, 6.258, 6.238, 6.225, 6.219, 
6.21, 6.213, 6.216, 6.216, 6.22, 6.222, 6.229, 6.233, 6.236, 
6.239, 6.238, 6.248, 6.258, 6.271, 6.292, 6.311, 6.33, 6.342, 
6.348, 6.358, 6.36, 6.365, 6.366, 6.359, 6.353, 6.342, 6.333, 
6.327, 6.33, 6.327, 6.319, 6.326, 6.332, 6.324, 6.34, 6.356, 
6.373, 6.402, 6.443, 6.487, 6.537, 6.571, 6.582, 6.582, 6.563, 
6.54, 6.515, 6.478, 6.442, 6.41, 6.372, 6.331, 6.304, 6.277, 
6.246, 6.218, 6.205, 6.199, 6.193, 6.186, 6.187, 6.203, 6.233, 
6.274, 6.315, 6.362, 6.4, 6.432, 6.459, 6.484, 6.512, 6.539, 
6.544, 6.548, 6.543, 6.529, 6.525, 6.593, 6.638, 6.713, 6.831, 
6.968, 7.142, 7.37, 7.656, 7.924, 8.117, 8.181, 8.262, 8.273, 
8.25, 8.243, 8.183, 8.13, 8.073, 8.021, 7.953, 7.888, 7.819, 
7.765, 7.733, 7.703, 7.675, 7.663, 7.661, 7.673, 7.701, 7.739, 
7.8, 7.843, 7.902, 7.973, 8.06, 8.136, 8.216, 8.342, 8.429, 8.585, 
8.694, 8.838, 9.026, 9.38, 9.815, 10.294, 10.786, 11.347, 11.859, 
12.233, 12.637, 12.966, 13.283, 13.685, 13.908, 14.334, 14.721, 
15.149, 15.581, 16.521, 17.244, 17.842, 18.501, 19.313, 20.18, 
20.831, 21.707, 22.559, 23.352, 24.222, 25.223, 25.933, 26.78, 
27.336, 28.231, 28.845, 29.255, 29.805, 30.559, 30.458, 30.79, 
30.01, 30.098, 29.579, 29.405, 29.149, 28.992, 28.879, 28.596, 
28.513, 27.866, 27.839, 27.721, 27.259, 27.385, 26.951, 26.759, 
26.467, 26.188, 25.971, 25.564, 25.572, 25.392, 25.243, 25.029, 
24.91, 24.723, 24.44, 24.286, 24.039, 23.907, 23.594, 23.454, 
23.31, 23.152, 22.881, 22.773, 22.481, 22.202, 21.956, 21.718, 
21.385, 21.212, 20.804, 20.526, 20.251, 19.879, 19.599, 19.357, 
19.033, 18.914, 18.647, 18.546, 18.301, 18.163, 17.975, 17.763, 
17.563, 17.43, 17.19, 17.061, 16.821, 16.673, 16.518, 16.312, 
16.137, 16.007, 15.833, 15.698, 15.528, 15.349, 15.195, 15.025, 
14.867, 14.718, 14.57, 14.357, 14.224, 14.021, 13.917, 13.79, 
13.584, 13.405, 13.267, 13.115, 13, 12.925, 12.786, 12.678, 12.518, 
12.44, 12.342, 12.221, 12.138, 12.006, 11.919, 11.84, 11.776, 
11.701, 11.605, 11.54, 11.484, 11.371, 11.321, 11.252, 11.177, 
11.123, 11.066, 11.028, 10.961, 10.917, 10.842, 10.808, 10.706, 
10.66, 10.588, 10.534, 10.496, 10.439, 10.434, 10.407, 10.393, 
10.326, 10.289, 10.243, 10.188, 10.134, 10.09, 10.07, 10.039, 
10.089, 10.19, 10.407, 10.695, 11.179, 11.769, 12.402, 13.126, 
13.95, 14.598, 15.244, 15.748, 16.186, 16.655, 16.938, 17.177, 
17.321, 17.365, 17.337, 17.256, 17.256, 17.163, 17.1, 17.143, 
17.363, 17.495, 17.883, 18.542, 19.075, 19.628, 20.129, 20.61, 
20.944, 21.508, 22.023, 22.557, 23.16, 23.827, 24.4, 24.849, 
25.24, 25.387, 25.282, 25.309, 25.296, 25.562, 25.898, 26, 26.274, 
26.225, 26.295, 26.394, 26.274, 26.071, 26.072, 26.035, 26.211, 
26.383, 26.303, 26.501, 26.474, 26.513, 26.728, 26.825, 27.036, 
27.121, 27.443, 27.65, 27.775, 27.689, 27.79, 28.197, 27.82, 
28.144, 27.998, 27.789, 27.686, 26.934, 26.954, 26.612, 26.222, 
26.192, 25.722, 25.616, 25.531, 25.292, 25.189, 24.797, 24.832, 
24.664, 24.525, 24.343, 24.419, 24.284, 24.044, 24.054, 23.818, 
23.651, 23.619, 23.587, 23.589, 23.397, 23.314, 23.144, 22.834, 
22.846, 22.571, 22.437, 22.204, 22.036, 21.734, 21.588, 21.283, 
21.018, 20.798, 20.394, 20.138, 19.926, 19.679, 19.477, 19.19, 
18.914, 18.683, 18.514, 18.243, 18.11, 17.981, 17.873, 17.723, 
17.655, 17.56, 17.496, 17.444, 17.353, 17.342, 17.289, 17.221, 
17.182, 17.05, 16.966, 16.87, 16.649, 16.514, 16.457, 16.305, 
16.172, 16.121, 16.223, 16.198, 16.412, 16.695, 16.984, 17.443, 
17.808, 18.403, 19.015, 19.509, 19.919, 20.47, 20.922, 21.258, 
21.561, 21.636, 21.557, 21.321, 21.223, 20.979, 20.834, 20.559, 
20.501, 20.434, 20.312, 20.226, 20.08, 19.971, 19.846, 19.8, 
19.712, 19.652, 19.59, 19.502, 19.442, 19.378, 19.261, 19.197, 
19.193, 19.159, 19.119, 19.053, 18.966, 18.916, 18.877, 18.774, 
18.71, 18.623, 18.501, 18.422, 18.277, 18.145, 18.057, 17.947, 
17.828, 17.73, 17.56, 17.472, 17.347, 17.187, 17.019, 16.896, 
16.784, 16.676, 16.496, 16.395, 16.255, 16.154, 16.125, 16.037, 
15.981, 15.889, 15.897, 15.811, 15.786, 15.723, 15.584, 15.535, 
15.433, 15.333, 15.291, 15.213, 15.091, 15.02, 14.928, 14.845, 
14.804, 14.916, 15.406, 15.627, 16, 16.414, 16.809, 17.147, 17.457, 
17.723, 17.973, 18.175, 18.371, 18.551, 18.613, 18.581, 18.389, 
18.036, 17.58, 17.179, 16.751, 16.425, 16.129, 15.928, 15.791, 
15.61, 15.487, 15.389, 15.363, 15.355, 15.312, 15.326, 15.301, 
15.324, 15.291, 15.266, 15.184, 15.102, 15.056, 15.008, 14.947, 
14.899, 14.84, 14.82, 14.819, 14.781, 14.766, 14.768, 14.715, 
14.696, 14.631, 14.54, 14.455, 14.344, 14.209, 14.103, 14.027, 
13.931, 13.848, 13.769, 13.662, 13.611, 13.493, 13.424, 13.358, 
13.286, 13.232, 13.132, 13.034, 12.98, 12.937, 12.86, 12.76, 
12.694, 12.604, 12.561, 12.466, 12.361, 12.257, 12.138, 12.025, 
11.95, 11.863, 11.767, 11.675, 11.554, 11.473, 11.38, 11.287, 
11.198, 11.125, 11.074, 11.007, 10.96, 10.906, 10.85, 10.768, 
10.693, 10.62, 10.513, 10.435, 10.33, 10.226, 10.147, 10.045, 
9.956, 9.844, 9.758, 9.669, 9.596, 9.542, 9.488, 9.453, 9.423, 
9.359, 9.331, 9.332, 9.307, 9.279, 9.242, 9.204, 9.147, 9.079, 
8.982, 8.892, 8.814, 8.74, 8.659, 8.602, 8.531, 8.45, 8.412, 
8.35, 8.284, 8.243, 8.202, 8.168, 8.133, 8.111, 8.08, 8.062, 
8.044, 8.024, 8.007, 7.975, 7.924, 7.867, 7.782, 7.71, 7.624, 
7.544, 7.463, 7.373, 7.297, 7.233, 7.166, 7.103, 7.052, 7.024, 
6.985, 6.938, 6.917, 6.914, 6.909, 6.893, 6.9, 6.903, 6.917, 
6.891, 6.853, 6.803, 6.749, 6.694, 6.639, 6.565, 6.483, 6.42, 
6.37, 6.32, 6.282, 6.252, 6.226, 6.204, 6.214, 6.215, 6.166, 
6.155, 6.134, 6.133, 6.158, 6.175, 6.181, 6.175, 6.167, 6.148, 
6.116, 6.082, 6.046, 6.019, 5.983, 5.962, 5.933, 5.912, 5.891, 
5.864, 5.85, 5.831, 5.822, 5.806, 5.806, 5.813, 5.828, 5.856, 
5.876, 5.907, 5.931, 5.97, 6.023, 6.055, 6.072, 6.069, 6.06, 
6.052, 6.028, 6.015, 5.987, 5.965, 5.937, 5.902, 5.869, 5.836, 
5.798, 5.77, 5.756, 5.767, 5.812, 5.869, 5.935, 6.029, 6.119, 
6.188, 6.235, 6.292, 6.332, 6.383, 6.455, 6.575, 6.634, 6.617, 
6.543, 6.441, 6.336, 6.241, 6.162, 6.08, 6.011, 5.942, 5.885, 
5.83, 5.785, 5.756, 5.729, 5.691, 5.666, 5.628, 5.581, 5.531, 
5.478, 5.431, 5.383, 5.327, 5.278, 5.23, 5.193, 5.159, 5.119, 
5.086, 5.057, 5.034, 5.016, 4.995, 4.912, 4.963, 4.987, 5.019, 
5.099, 5.21, 5.313, 5.476, 5.692, 5.883, 6.152, 6.457, 6.633, 
6.623, 6.445, 6.218, 5.996, 5.813, 5.667, 5.548, 5.461, 5.379, 
5.303, 5.24, 5.168, 5.122, 5.078, 5.044, 5.004, 4.973, 4.943, 
4.911, 4.875, 4.848, 4.823, 4.794, 4.772, 4.75, 4.727, 4.711, 
4.693, 4.668, 4.652, 4.639, 4.627, 4.617, 4.608, 4.593, 4.573, 
4.56, 4.549, 4.544, 4.541, 4.532, 4.512, 4.504, 4.493, 4.474, 
4.465, 4.45, 4.438, 4.417, 4.407, 4.396, 4.387, 4.381, 4.375, 
4.361, 4.351, 4.337, 4.334, 4.33, 4.325, 4.32, 4.311, 4.312, 
4.305, 4.291, 4.274, 4.257, 4.248, 4.233, 4.23, 4.222, 4.216, 
4.215, 4.2, 4.19, 4.184, 4.177, 4.172, 4.161, 4.152, 4.145, 4.141, 
4.136, 4.133, 4.126, 4.114, 4.099, 4.087, 4.078, 4.064, 4.05, 
4.043, 4.035, 4.025, 4.013, 4.002, 3.989, 3.979, 3.97, 3.966, 
3.958, 3.943, 3.94, 3.932, 3.928, 3.918, 3.91, 3.901, 3.88, 3.874, 
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3.731, 3.724, 3.723, 3.72, 3.72, 3.709, 3.707, 3.709, 3.707, 
3.685, 3.668, 3.667, 3.682, 3.671, 3.652, 3.644, 3.635, 3.632, 
3.626, 3.617, 3.614, 3.604, 3.598, 3.591, 3.586, 3.58, 3.578, 
3.57, 3.564, 3.558, 3.547, 3.534, 3.524, 3.514, 3.499, 3.481, 
3.476, 3.459, 3.449, 3.44, 3.43, 3.414, 3.41, 3.411, 3.417, 3.431, 
3.455, 3.496, 3.53, 3.568, 3.604, 3.645, 3.685, 3.717, 3.728, 
3.727, 3.69, 3.635, 3.592, 3.558, 3.52, 3.498, 3.472, 3.44, 3.413, 
3.393, 3.37, 3.353, 3.321, 3.287, 3.261, 3.24, 3.237, 3.23, 3.227, 
3.225, 3.223, 3.233, 3.242, 3.247, 3.234, 3.208, 3.181, 3.154, 
3.134, 3.123, 3.109, 3.097, 3.091, 3.091, 3.085, 3.08, 3.074, 
3.073, 3.07, 3.046, 3.052, 3.053, 3.049, 3.046, 3.029, 3.028, 
3.018, 3.003, 2.997, 2.981, 2.971, 2.957, 2.946, 2.937, 2.931, 
2.926, 2.916, 2.907, 2.904, 2.893, 2.887, 2.876, 2.866, 2.861, 
2.854, 2.851, 2.85, 2.855, 2.865, 2.86, 2.859, 2.855, 2.843, 
2.838, 2.828, 2.806, 2.793, 2.782, 2.775, 2.77, 2.759, 2.752, 
2.744, 2.737, 2.729, 2.723, 2.719, 2.711, 2.703, 2.693, 2.697, 
2.7, 2.699, 2.695, 2.693, 2.693, 2.692, 2.69, 2.681, 2.67, 2.658, 
2.642, 2.637, 2.63, 2.623, 2.614, 2.611, 2.604, 2.604, 2.598, 
2.591, 2.593, 2.594, 2.591, 2.585, 2.602, 2.601, 2.597, 2.59, 
2.583, 2.582, 2.569, 2.562, 2.551, 2.544, 2.536, 2.537, 2.523, 
2.516, 2.513, 2.515, 2.516, 2.516, 2.519, 2.518, 2.517, 2.516, 
2.52, 2.534, 2.566, 2.607, 2.625, 2.675, 2.703, 2.742, 2.782, 
2.827, 2.956)), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA, 
-1297L))

You could set the size of the zoom panel relative to the main plot via the argument zoom.size which defaults to 2, i.e. the zoom panel is twice the size of the main panel. Hence, to achieve your desired result set zoom.size=.5:

require(dplyr)
require(tidyverse)
require(ggforce)
DebitH %>%
  ggplot(aes(x = Date, y = Débit_horaire)) +
  geom_point(alpha = 6 / 10, size = 0.3, color = "blue") +
  geom_line(alpha = 4 / 10, size = 0.5, color = "blue") +
  labs(x = "Date", y = "Débit Horaire (m3/s)") +
  theme_bw() +
  theme(
    panel.grid.major.y = element_line(
      color = "grey",
      size = 0.25,
      linetype = 2
    ),
    legend.position = "none"
  ) +
  facet_zoom(xlim = as.POSIXct(c("2021-01-15 00:00:00", "2021-02-15 00:00:00")), zoom.size = .5)