Please find enclosed the preliminary translation of the Administrator interface. Many thanks to Pascal Montagne, he contributed half of the translation.
The tar file should be expanded under /opt/zimbra/apache-tomcat-5.5.15/webapps/zimbraAdmin/WEB-INF/classes/msgs.
ZMsg and AjxMsg are the same as for the regular interface.
Observer that the *_fr* files are soft links to the *_fr_FR* files. In principle only the *_fr* files are needed to automatically use French if the browser language is French, but I include both file names just in case.
Remember to restart Zimbra and empty the cache of your browser before testing.
If it doesn't work and you don' t need multi-language support, just copy the *fr_FR* files over the English files.
If you have problems downloading the attachment (it takes some time for approval), you can download it from http://files.whitehatmail.fr/ with user "invite" password "invite".