It seems that Opus is not able to open .XIP archives?
If you can open then in 7-Zip, and point us to an example one, then we should be able to make them work in Opus.
The file is Xcode_13.2_beta.xip (10 GB). You can download it from the XCode website.
BTW, it took 20 minutes to extract it in Finder (by double-clicking it).
Any sample files that aren't 10GB and don't require giving my phone number to Apple? 
Have you tested that 7-Zip can open the archive? If it can't then this would be too much work to implement.
This 2020 thread suggests 7-Zip can't open XIP files, unless the poster was mistaken: how to open XIP file in windows | Apple Developer Forums
This older thread suggests 7-Zip may have been able to open it, but I'm not sure if it was hypothetical (with some code changes) or if it actually worked. It sounded like it was hypothetical. Neither of the links to example XIP files still works (or has a XIP file at the other end that I can see): 7-Zip / Discussion / Open Discussion: [REQ] Add support for xip archives (variant of xar)
This format seems quite rare as it's hard to find examples of it on the web.
