Apologies, it’s just a quirk of the system that Arc uses to upload the game here.
For some damn reason, every now and then it decides to put the apk inside a zip file.
You’ll need a file manager that can extract zip files (I recommend Solid Explorer) and extract it.
Or you can also use the downloads in the public posts on Patreon and Subscribestar. It’s the same version as the one posted here.