My setup integrates SAMBA with Zimbra LDAP using the method outlined here:
UNIX and Windows Accounts in Zimbra LDAP and Zimbra Admin UI - Zimbra :: Wiki
The extensions zimbra_posixaccount & zimbra_samba have been installed and work well with any Global Admin account. Delegated Admins with default domain admin rights are however not able to manage POSIX and SAMBA groups even after granting them permissions to read/write LDAP attributes following steps outlined under Using delegated administration feature with posix/samba integration of the same document. The POSIX and SAMBA extension tabs appear including the list of groups already created by global admin, but none of the LDAP attributes granted to the delegated admins appears.