ragnarok2040 has updated the zlib library port to PS2.

Release notes:

I updated the zlib port to version 1.2.3. It’s at http://homebrew.thewaffleiron.net/ragnarok2040. I made a patch as well so updating the svn repository should be easier. Not much work was really needed except for reorganizing the directory structure of the files and copying over the Makefiles from the old port.

http://forums.ps2dev.org/viewtopic.php?t=11247