We do a configuration where a windows server is used as a dhcp with multiple scopes, and we have multiple ESSID's VLANed so each ESSID receive DHCP from their specified scope. I am sure there are other ways to do this.
The ZoneDirector can serve DHCP on it's local subnet only, and the ZoneDirector assumes it's using default VLAN 1 (considered 'untagged'). Best practices advise customers to assign unique/different VLAN IDs to their WLANs (clients), and this requires that the ZD be connected to a switch that can Trunk more than one VLAN, each with its own DHCP server and def-gw IP for those subnet(s). The ZoneDirector local DHCP is meant to provide a local IP to APs that are initially being connected (to learn ZD IP or Mesh info, and then can be deployed remotely), *or* for the small business/home user, who trusts his wireless clients not to mess with his ZD/APs.