I just noticed in browsing that "henoheno" released a ZIP support library.
http://psp.holybell.to/uploader2/upload/UnzipSample.zip
There is a demo EBOOT.PBP along with the source.
Currently, there's a size limit of 6MB (Memory buffer issues), and it uses the zlib libraries found @ http://hp.vector.co.jp/authors/VA016379/cpplib/zlib.htm
Place the EBOOT in a folder called "Unzipsample" (required for output)
Tested with a zipped GBC ROM, it outputs it to "out.dat" just fine.
This should create new possiblities for emulators and such.