Mac CardDAV support depended partly on an update from Apple which seems to have just appeared as part of OS X 10.6.3. See
Bug 22008 – WebDAV: Add support for CardDav and be aware that when filling in the CardDAV server field, you need supply the port. Thus zimbra.company.com:80 or zimbra.company.com:443.
For LDAP in Address Book, I've only had luck using anonymous connections. To turn this on with a fresh install of 6.0.x, see
Bug 15378 – Obviate the need for and disallow LDAP anonymous binds but be aware that you should firewall off LDAP from the outside world if you do this, or spammers will be able to harvest all your email addresses easily.
See also
Disable Anonymous LDAP Browse where I've posted my efforts, so far unsuccessful, to do secure authenticated connections from Address Book to Zimbra LDAP.