So this should be a simple one.

Put a uart into the case. It needs to have a micro-usb socket for neatness. So I pulled a CP2102 module out of the stock. But the case is shallow, and the header pins stood straight up. A great return to old desoldering practices were required to remove the 2x5 straight pin header and replace it with a 2x5 right angle header. As you can see from the photo, it was nicely done.

Only problem is that these modules are 5v only. And while the Pi Zero pins may or may not be 5v tolerant, I didn't have room for a level shifter. After all that work, I managed to find my 1 remaining FT232 hiding in the box of another non-completed project and used that instead. It already had a right angle header, so no mod necessary. Doh. Then promptly ordered more FT232 modules from AliExpress.

Given these modules have a 5v/3.3 volt selection made by a vertical jumper, to reduce height i cut off the header, and bridged the 3.3v with solder from underneath.