APs always compare their running image to the version on the ZoneDirector, and will upgrade/downgrade to the ZD's version. Be sure then, that the ZD release supports all models of access points.
The Monitor/Access Points page will show if all your APs are in Connected state, and if you click any AP MAC address the AP details will show the firmware running on the AP.
In the virtual SmartZone platform, SCG/vSZ-H which support multiple tenant domains, can have different AP versions. You view the AP Zones, click on the AP Zone to drill down, to see the AP version (and a button to change it if desired).