Have you tried redownloading it to verify it downloaded correctly? I can unzip it fine. (I'd tell you to make sure it's opening with Archive Utility, but I assume you're tech-literate if you found this game lol.)
That would be weird, because I can unzip it fine. Things to check include:
- Redownloading the file to ensure it didn't get corrupted during download
- Checking system storage to ensure it can get unzipped fully
- Using a different unzip utility
- Downloading from another source (two mirrors are provided in the game's Patreon) in case it's a problem on itch's servers