Default utility for Zip files?

I've installed third-party software (Calibre) that keeps setting itself as the default program to open Zip files on my MacBook (Monterey 12.6). I keep telling my Mac to use Archive Utility as the default for Zip files, but the Mac keeps reverting to Calibre as the default. Calibre technical support insists this is an Apple/Mac issue, not an issue with their software. Any suggestions?