If the AP network can talk to the ZD network, configure the DHCP server on the AP network with Option 43 pointing to the ZD's IP address.
See our knowledge base article "Registering an AP with the ZoneDirector",
https://support.ruckuswireless.com/answers/000001255 Another way to "prime" your APs, is to bring them up initially on the ZD network, so they're updated/configured, and then deploy them remotely
and they will "know" the ZD to try and connect back to.