I've been using that zLib library for a while now, really easy to use, and fast too.

I wrote a small program that searches in a directory and compresses all uncompressed files. In this case I made it search for all xml files (meshes, gui's, etc) and automatically compress them.

So when creating meshes you'd just work with them normally, and when you make a release you run the program, and it'll compress all the files.

It could also be used to compress textures and stuff aswell.

Not sure if the library could be some how ported to python.
Or even get the bpython script to run a program written in delphi to compress the file after it's been made?