How to calculate the delta between the previous period and the current period in DAX with an IF

I am trying to calculate in DAX the delta between the previous period (quarter) and the current period, but my formula does not work correctly for each case

I try to calculate the difference between Value and Q-1 Value when there is a result in Value <> 0 Then I try to calculate the difference between the Sale and the Value Q-1 when there is no result in Value = 0

To resume, here the formula explained

if the Value <> 0 => take the current Value - the Value of the previous Quarter else if the Value = 0 (case of a Sale) => take the sale - the Value of the previous period

I didn't succeed the second part of the if, it only shows the value of the Sale in current quarter

Here is the code I used:

Calculate =
IF (
    SUM ( 'Append'[Value] ) <> 0,
    SUM ( 'Append'[Value] )
        - CALCULATE (
            SUM ( 'Append'[Value] ),
            PARALLELPERIOD ( 'Append'[DATE_REFERENCE], -1, QUARTER )
        ),
    CALCULATE ( SUM ( Append[Sale] ), KEEPFILTERS ( 'Append'[Status] = "Sale" ) )
        - CALCULATE (
            SUM ( 'Append'[Value] ),
            PARALLELPERIOD ( 'Append'[DATE_REFERENCE], -1, QUARTER )
        )
)

1. if the Value <> 0 => take the current Value - the Value of the previous Quarter

2. if the Value = 0 (case of a Sale) => take the sale - the Value of the previous period```

Here is the result :

Here is the result I would have :

Could you please help me ?

Many thanks in advance

Using the code sent by Michal, I tested different formulas and now it works, I added the line "ALLSELECTED('Append')" followed by the line "PARALLELPERIOD('Append'[DATE_REFERENCE], -1, QUARTER)"

This line allows me to select all the values, even those that were previously filtered and not retrieved by "PARALLELPERIOD"

Here is the code

CalculateMeasure = 
VAR CurrentValue = SUM('Append'[Value])
VAR CurrentSale = SUM('Append'[Sale])
VAR PreviousQuarterValue = 
    CALCULATE(
        SUM('Append'[Value]),
        ALLSELECTED('Append'),
        PARALLELPERIOD('Append'[DATE_REFERENCE], -1, QUARTER)
    )
RETURN
    IF (
        CurrentValue <> 0,
        CurrentValue - PreviousQuarterValue,
        IF (
            CurrentValue = 0,
            CurrentSale - PreviousQuarterValue,
            BLANK()
        )
    )