Ruby on Rails - Zip/HTTParty

I have an api request that returns multiple (Word) files to-be-downloaded, but I can't send_data IN the while loop, else I'll get the dreaded Multiple Renders error, so my question is how can I package/combine/zip/parse the multiple so that I can send_data just once?

Here's the block:

def generate_multi_letter(template, letterName, params)
@Document_URL = "#{ENV["API_HOST"]}/api/StateDocument/GenerateDocX/#{template}"
response = HTTParty.post(@Document_URL,
                         :body => params,
                         :headers => { "Content-Type" => "application/json" })

Zip::InputStream.open(StringIO.new(response)) do |io|
while entry = io.get_next_entry
            report = io.read
            send_data report,
              :filename => letterName + ".docx",
              :type => "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
              disposition: "attachment"
          end

#or maybe something more like.....?

Zip::File.open(response, Zip::File::CREATE) do |zip|
  Attachment.all.each do |attachment|
    file = Tempfile.new("#{attachment.created_at.in_time_zone}.docx")
    file.write(attachment.image_string)
    zipfile.add("#{attachment.created_at.in_time_zone}.docx", file.path)
  end
end

zip_data = File.read(response)
send_data(zip_data, type: 'application/zip', disposition: 'attachment', filename: letterName + ".docx")

I'm also getting "path name contains null byte" errors, if anyone spots where I'm going wrong there??

For any who follow, this turned out to be surprisingly easy, just trust the browser, and return the whole response (so long as you define the mime type as .zip):

@URL = "#{ENV["API_HOST"]}/api/GenerateDocX/#{template}"
response = HTTParty.post(@URL,:body => params,:headers => { "Content-Type" => "application/json" })

send_data response, :filename => letterName + ".zip", type: 'application/zip'