Nearly done with my second (!) GBCZ.

My goal this time (aside from using up some of the extra parts I bought the first time around) was to make it as "clean" as possible, which meant, in part, designing a 3D bracket to hold the pi on the front of the shell, so I could keep the screen and button board wires as short as possible. And since there was some room there around the pi, I also put some spots to mount the rest of the components, except for the PSU which would still mount in the cartridge area (and I used a real Game Boy Color game cart this time, which were all transparent, so you can see the status LEDs without having to drill anything anywhere, but I did cut out access to the micro usb charging port there). I also did up some 3D-printed mounts to hold soft press tactiles in the front, to use Game Boy Pocket buttons in the rear, and they just clip on the board, which is pretty neat (I put a little glue in to hold them, but they really didn't need that).
Since I freed up some room by keeping wires short, I actually fit a 4000mAh battery in the back !!!


The parts were basically the same as my first one but instead of I2S audio, i went with mono PWM and used Pocket Adventures filter and Adafruit's 8302a amp. I2S was definitely better sounding, but this works, and it was a couple less wires to connect. I was also hoping the PWM would be better performant than I2S, but that I can't tell for sure yet. I also found this navigation toggle which I'm using for the volume up and down, as well as the button monitor / hotkey.
A couple other notes... I was able to put a barrel jackin the original location, near the headphone jack, and all the front buttons are GBC ones that I sanded and polished the "a" and "b" off of. The screen protector is a mirrored plastic one (hard to take pictures of that don't turn out to be selfies), which I might swap for a glass one at some point if I find one that works well, but I tried a few different ones, and this one looked best (even though there are a couple scratches off to the side from bouncing around a parts box) so I might stick with it. Frustratingly, this shell isn't totally flat, and the protector has a tendency to pull up in one corner.
onto somm more pics... I will add in more details later.
here are the models I made and used, except for the front X/Y button wells. I used GBC buttons and modified this model but I wasn't really that happy with the results. I would recommend using GBP buttons and the well that I used on the first build instead.
For the shoulder buttons, I just kind of eye-balled the spot, but it lines up to just on the "outside" line of the wall where the game cart would normally sit, and then just to the bottom of the text that was printed onto the shell, above the battery compartment (hopefully that makes sense, but I'll try and add in some more images that illustrate that better).