Hi Rob,
sorry for my late reply. I was out of office for some days.
Pi Zero W cannot be updated with a newer release of rooExtend. It is a ARMv6 and the new release is for ARMv8 processors only. Pi4 and also Zero W2 will work with the new release but Zero W no more.
But please be careful regarding Roon/rooExtend and WiFi. Roon don’t recommend it and the past showed that weak WiFi leads to connection breaks and restart on rooExtend.
So my opinion: It’s more stable using an Ethernet cable to the Raspberry Pi.