I am having this problem as well - just installed the connector.
The registry value specified is 3, but we cannot seem to connect to the shared addressbook iin Outlook. I have tried accepting the share in the web interface, but it still does not show up in oUTLOOK. There is no Zimbra Connector listed in the com add-ins on one workstation.
I don't know if it matters, but in COM Add-ins on my machine that is working fine I don't have Zimbra Connector either. I DO have Zimbra Client Extension under the Add-In Manager though. Maybe run a search on the wiki? I seem to recall there were some instructions for reseting some stuff to make the connectors work right (like checking Disabled extensions, etc).