Just got DietPi running on my Radxa Zero 4gb ram, 16gb emmc. I flashed the Debian image https://github.com/radxa/radxa-zero-images-released/releases/tag/radxa-zero-v20210930 to the EMMC then followed the instructions on the DietPi website for creating your own image. Basically just SSH into the fresh Debian install on the Zero and copy and paste to run the scripts.
Everything seems to work okay, so I figured I would share with y’all.