If you don't care to mess with your file association settings, then the old-fashioned way of just opening Winzip directly and using "File | Open Archive" from the menu (or the equivalent toolbar button) and browsing to it directly works just fine.

I was prompted to pick a name for the uncompressed file in the archive, complete with a suggestion. I obviously chose to just change the extension to '.PZ3'. BTW, since there isn't any path information stored with the .PZZ there isn't any need to worry about whether or not the 'Use Folder Names' box is checked or not when you uncompress it wherever.

I hope that's helpful for someone.