But this should already be installed by default! (if I try to remove it, zypper wants to uninstall most of my system: 1 Paket wird aktualisiert, 7 werden zurückgestuft, 1 neu, 3838 zu entfernen, 7 Anbieterwechsel…)
Why do you think you need to install it?
We are lucky enough to have an Open Source Lab, I will test all suggestions and report back here. I’m not sure why Joomla 3.1 say it is not installed.
Doing the same installation on Mint however works without any problems, that is why I think zlib is not installed on Suse 12.3. Will test and let you know, my first problem was that I tried to install zlib not libz1.