We have created a thread about the issue which seems to be affecting other games as well:
https://itch.io/t/3305483/zip-files-getting-corrupted-on-download
The solution is to click the "Downloads not starting?" link and switching to alternate download mode.
The only con is that the download speed is capped at 8mb/s.
If you rather try another host until the issue is fixed, the links in my patreon page (MEGA and Pixeldrain) might offer better speed.