So first you need to download the 104.x.x.x software from the support portal so you have a version then that can connect to the ZD and SZ/SCG/vSZ
Factory reset the unleashed AP and in the first screen you can select to upgrade the AP, use this to flash the 104.x.x.x code on the AP.
After that the AP will reboot. login to the webgui and set the controller IP, or use DHCP option 43 or via CLI set director x.x.x.x
Then the AP will be connecting to the ZD and will join it and get the ZD software.