There are some notes on the download page for the Zimbra Server Info module about the need to install zimbraAdmin. I have tried to contact Ron to ask if I could include his code with mine, to simplify installation, but I have not had a reply as yet.
"Ron's code and examples can be download from
ftp://ftp.rongage.org/pub/zimbraAdmin, this should be uploaded to the Joomla /includes/zimbraAdmin folder for this module to work"