ZIPX is a modern variant of ZIP archive format used by Corel WinZIP and it is actually this software if you want to repack your standard ZIP archive to ZIPX format, which is pretty much what zip to zipx conversion represents.
The modern format has perhaps a bit better compression ratio that might be noticeable on very large files, or packages with a large number of small files, but otherwise there won't be much of a difference.
Updated: October 10, 2023