You can configure zones at WLAN/SSID level and at AP level.
If the SSIDs don’t have a zone configuration, then it will be broadcasted by all the APs irrespective of the AP zones.
For example
SSID-1, zone= <empty>
SSID-2, zone= room2
AP1, zone = <empty>
AP2, zone = room2
Then you’ll see SSID1 and SSID2 being broadcasted on AP2, and SSID-1 being broadcasted on AP1
Now if you change SSID-1, zone= room1 and AP1, zone = room1
You’ll see SSID2 being broadcasted on AP2, and SSID-1 being broadcasted on AP1