I have searched the forums and as far as I understand Zimbra does support iPhone, Sunbird and Thunderbird with LDAP.
Actually I only need somebody confirming me that all these features are supported
- Thunderbird (IMAP)
- Thunderbird shared addresses (LDAP I assume) with write permissions
- Sunbird shared calendars with write permissions
- iPhone with ActiveSync (Calendar, Mail, Address Book) with write permissions