I figured I'd ask here first, but asking them to help would be a good idea too.
The compression algorithm that is used is just Zlib; in fact, I'm using Compress::Zlib to do the actual (de)compression. What A::Z does is to handle the archive part (as well as making it easy to do compression, decompression, building archives, etc.).
Re^2: Seeking a maintainer for Archive::Zip