MegaDrive Emulation is fine on the Original Pi which negates the need for a Pi Zero. I would advise a version of PicoDrive which is the best overall MegaDrive/Genesis Emulator available for the Pi. Check the Emulation sticky for info -
Link - viewtopic.php?f=78&t=54357
How is PicoDrive, an outdated, buggy and unaccurate emulator, the best available on the Pi?
The only thing that emulator does well is running fullspeed on a Pi1 (provided you use laggy GLES graphics. Framerate != input lag).
Simply load Sonic 1 (Master System) and jump. If you have ever played that game, you will notice the PSG audio (which is also part of the Sega MegaDrive/Genesis sound system) is utterly broken.
Load Golden Axe (Mega Drive) and look for the palette problems during demo mode.
Load Sonic CD and leave the music track playing in Palmtree Panic: you will see looping at the end of the song is broken.
The same with Lunar and many other games.
PicoDrive is abandoned and broken.
For an accurate Sega emulator, use Genesis PlusGX core with RetroArch, be it in Lakka, RetroPie, Recalbox or whatever. But DON'T use PicoDrive.