Maybe not completely Android-specific, I don't think you can add a patent by identifier to Zotero on any platform. The proper entry method is certainly to search for the patent on Espacenet, Google Patents or another supported site and capture it from your browser.
The proper entry method is certainly to search for the patent on Espacenet, Google Patents or another supported site and capture it from your browser.
So if you are really only using Android, I guess the only option here is a 100% manual entry, unfortunately.