After thinking it wasn’t possible, thanks to Micro Linux YouTube channel I have got Armbian running on the the EMMC and Manjaro going on the SD card.
Like Micro Linux, my boot to USB button was unable to produce the desired result to allow me to erase the EMMC.
I followed his clear instructions using a serial cable and Minicom, instead of Putty, to erase the boot loader. I then put Armbian Jammy on to an SD card and was able to boot to to the card. Then using Armbian-config on the running SD card instance, I installed/copied the Armbian instance to the EMMC.
After a few restarts, I pulled the SD card and the Zero booted off of the EMMC. Next I loaded an image of Manjaro on to another SD card. I shutdown the Armbian instance on the EMMC and inserted the Manjaro SD card. Following an initial lengthy delay the Zero booted into Manjaro. I then shutdown Manjaro, pulled the card and powered back up agai. Voila, i am back into Armbian.
Chances are good I will break this again…but for now I am happy…
Also when running Manjaro off of the card the EMMC shows up as a mounted drive.
Thanks Micro Linux…