Hi, I've made a catalan translation for Zimbra, for in-house needs.
It's based on Open Source Edition, I don't know if the language files for other editions are the same.
Installation instructions are included in the file (readme)
Please let me know if it's helped you, or if you've had any problems with it.
Edit: November 4th
New version, corrected some mistakes, added some files:
deploy.sh (sample deployment script, read & edit before using)
Edit: February 4th, updated to 5.0.12
Updated all files to keep up with the modifications since the original release (mostly new text lines).