Recently bought a R500 with firmware 18.104.22.168.1347. Tried to "join" it to the ZD1106 but failure to update firmware 22.214.171.124.14. I know that one can't downgrade the R500's firmware. Would updating the ZD's firmware help? if so, what's the best version that can support the R500's 126.96.36.199.1347? 188.8.131.52.63?
If you go to Administer -> Upgrade, there should be a link in there that shows which models that firmware supports. If R500 is there, then all you need to do is to downgrade your WAP to 100.x.x firmware. Firmware is firmware and downgrading/upgrading it should not be an issue. Once the WAP joins the ZD that firmware gets wiped and 9.8 version of it gets installed.
I manage to downgrade the R500 to 100.1.0.0432 from 104.x.x and tried connecting it to ZD, still being prompted that it can't "update" to 9.8.x.x I will tried to find another 9.X version and downgrade it further if possible.