Currently, Ark uses The Unarchiver (unar) to open RAR files only, but unar can extract ZIP files as well, and is able to handle the filename and password encodings. This will be useful for Bug 393901, Bug 324978 and Bug 378904.
We have already 3 different backends to handle ZIP files and that's already hard to handle. This would complicate things a lot. We should try to focus on the libzip backend, instead.
I played a bit with The Unarchiver with zip files. One nice feature is that The Unarchive does its own encoding probing which works quite well on some archives. So while my concern about addition complexity is still valid, it might still make sense to add zip support to the unarchiver plugin.