The documentation of the zlib module is a little bit
out of date:

Version 1.1.3 is the most recent version as of
September 2000.

This is wrong, the most recent version of zlib is:
1.2.1

Change it to:

Version 1.2.1 is the most recent version as of October
2004.

source:
http://www.python.org/dev/doc/devel/lib/module-zlib.html

I hope python 2.4 Release will use this version.
(it is out since end 2003)