Hallo Gerald,
1. install php5-ldap on your server:
sudo apt-get install php5-ldap
2. add samba4 ldap port (tcp/udp 389) to internal firewall rules
3. enable ldap app in owncloud:
(Apps Sidebar→Apps, choose LDAP user and group backend, click on Enable)
4. add new ldap server config (change your Domain Administrator password!)
see my example test config in attachment
your CN-DN settings in Zentyal:
Users and Computers → LDAP Settings → LDAP information
Greetings from the foggy and frosty Bavaria!
julio