How come the android downloads a zip file now instead of an apk?
Apk file in that zip file, just open it and instal the apk
if installation difficulties begin, then I recommend moving the apk file from the zip file along the path "download"
The best way to download the .zip file is to download it from a PC or laptop and extract it from there and transfer the apk to your Android.
Because Butler (the Itch uploader) does it randomly and nobody can figure out why.