The Zip files created by DEXplor are true Zip files and are compatible with other software (winzip, pkzip, etc).
I defaulted to maximum compression and did not provide an option to use a lesser compression. I will probably add that capability in the future because it will be pretty easy to implement, although most people will still use max compression.
Moose, Zip uses zlib compression. Think of a zip file as a conglomeration of gzipped files with additional file attribute info (like the path, modified date, time, etc). So you will see the exact same compression between zip and gzip when using the same compression level. Of course there is a small amount of additional overhead in a zip because of the extra info per-file it stores, but it is a small amount, and is not dependant on the size of the original files.