Been trying to upgrade the firmware so it can support later T310 series APs as they are not showing on Monitor>Access points to connect them to the Zone director but it just seems to be stuck on uploading no matter how long i wait.
The ZD1200 10.1.0.0.1515 also supports the T310s/n/c/d model APs, so your APs should be able to recognize the ZD and join ok. You can then do another Backup/Upgrade to 10.3 (GA) if you want to be on our latest, most feature rich level software.
ZoneDirector best practices are to save a Backup from your current version, and add digits into the filename to remind you what version it came from. If you ever have to/want to downgrade, you can restore the backup from that previous release of software. Do this with each version upgrade.