Unfortunately, iOS does not allow you to download ZIP and you have to use third-party apps to evade this limitation. Probably the only easy way to download ZIP files is to use the Chrome app and a ZIP opener app.
- Download the Chrome app and any app that can open ZIP files
- Open the Chrome app, go to ZIP file detail and click
- The Chrome download page will show up. Click on
in the bottom right corner. The ZIP file will start downloading.