You can disconnect the AP/ZD communication while you upgrade ZDs, and APs
will upgrade to whatever version the ZD is running. (sometimes faster process if
upgrading more than one version).
Upgrade procedure should start at Administer/Backup page, and save a copy of
your current ZD configuration. Add digits like '82207' to the file to remind you what
version the backups came from, in case you need to downgrade.
Otw, you may also need to clear current alarms/alerts and reboot to free up memory
for a ZD1K upgrade (only the first one). Run a continuous ping to the ZD's IP addr
as it upgrades, so you know when it reboots to load the new version. If the ZD
screen doesn't take you back to Login page after 5 minutes after you saw pings
miss, click the URL on the screen to get to the Login page. See Monitor/Access
Points to watch APs go thru firmware upgrade, to disconnected when they reboot,
to provisioning and finally Connected states again.