Thumbs Up to everything Max said above. Follow the Release Notes, and those are valid versions for
upgrades with both APs supported. I add a tip to include digits in the ZD backup filenames, that identify
your version(s) saved from, in case you need to roll back or have any problem with upgrades.
And like Max said, of the EOL (Legacy) model APs, only a handful are still supported in latest ZD 10.0 (GA)
firmware and later releases.
https://support.ruckuswireless.com/documents/1608-zonedirector-10-0-ga-release-notes