We have a very basic library for handling Zip archives (which is built on top of the zlib support in Foundation). For documentation, please see http://www.appinf.com/docs/poco/
We currently have no plans to license this separately, as its mainly intended for use by the OSP (Open Service Platform), which uses Zip files as file format. Also, it does not support all specified Zip compression algorithms, so it's in no way meant as an universal Zip package. If you're interested, mail me at guenter (at) appinf (dot) com.
Another option would be to hack up your own file format, using the zlib classes for compression and the MIME multipart stuff in Net to combine multiple files into some kind of archive (create a MultipartWriter and connect it to a DeflatingOutputStream).