You will lose the configurations, the wlan settings, ap groups, everything. But the APs will remember what the ip address was of the ZD they used to attach to, so they will send a join request to the ZD as soon as the ZD is available again.
I think the factory defaults will set auto-approve the APs. If not you can tell the ZD to do that by going to Configure - Access Points - Access Point Policies.
If you want to keep some settings, you can make a backup, do factory defaults, and do a partial restore. That would be one of these:
- Restore everything.
- Restore everything, except system name and IP address settings (for failover deployment at the same site).
- Restore only WLAN settings, access control list, roles, and users (use this as a template for different sites).