Simple Raspberry Pi Zero case, which was designed to fit on the Ender 3's 40mm wide left hand side base extrusion next to the original electronics case to easily reach the printer's mainboard with a UART cable.

There is a plenty of space over the GPIO headers and its wires, it will protect these during usage.

The case can be mounted with M3 or M5 T slot nuts to any extrusion through the holes on the bottom part - or to any flat surface with 2-sided tape or - if you want to remove it sometimes - with M3 SHCS screws throughout the keyhole cutouts both vertically or horizontally.

It has cutouts for the HDMI, USB, display and SD connectors and there is an extra cutout for any kind of cable (e.g. UART cable).

The model requires 4pcs of M2.5xD3.5xL5 heat set inserts for fixing the Pi itself (with M2.5x6 SHCS), and 4pcs of M3xD5xL4 inserts for fixing the top cover to the bottom (with M3x12 SHCS).

There is 5mm between the Pi's bottom surface and the Bottom part's flat surface, which is more than enough even for the M5 screws. But make sure your fixing screws are not reaching the Pi (e.g. too loose screw, washers under the head, etc.)!