ZMZ combines the GUI of ZSNES with a Libretro backend; this allows people who like ZSNES' interface but dislike its poor emulation accuracy to get the best of both worlds.
It ships with an intermediate Snes9x version (newer than 1.53) by default; if it's too slow, try Snes9x-Next, or if you prefer bsnes, grab one from the same source. Note that some features, like layer toggle and SPC dumping, may not work with non-default cores.
It is also only compatible with x86 cores; ignore x86_64 cores even if you have a 64bit cpu. To switch core, go to Misc->Libretro.
By the way, of out pure curiosity, I loaded in an NES core from Libretro to see what would happen and I was quite astounded.
Edit: It also works with Metroid Fusion and Metroid: Zero Mission (VBA-Next core); Tetris and Mike Tyson's Punch Out (FCE Ultra core). NES games are stretched to the point of being unplayable, but work. It crashed marvelously with the two DS ROMs (Ace Attorney: T&T and Brain Age, with a DeSmuMe core) and any Pokémon ROM I tried and it black screened on Life and Death 2: The Brain (DOSBox core, not that I expected it to run). So yeah, you can use this as quite the good GBA emulator. NES too if you find a way to fix the screen resolution.
I notice that the L+R/U+D D-pad option doesn't work. When holding left AND right, the player simply walks right, which is normal, but when riding yoshi, the glitch is supposed to make yoshi keeps turning around as he "slides to the right".
I tried it, and I must say, pretty good for accuracy and stability, but the audio in my opinion is step back from ZSNES because it crackles constantly, and is very irritating. I know for a fact that other users are experiencing the exact same issue, as I read this emulator's tool release thread. But is there any setting that would fix or at least lessen the audio problems? If not I shall learn to tolerate it as best I can.
Found a problem: the recording function in the misc menu is broken, after you record, hitting ”play" button doesn't play what you have recorded, rather play afterwards. Unlike ZSNES. Another problem is that the fast forward is much slower than ZSNES, even when the max frame skip is the highest value possible.