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 the latest version of the Snes9x core as of 04/04/19 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.
Not sure on what technical aspects I should write here but... ok.
Tested with Windows 10 in an Acer machine, core i5 processor. The program simply crashes after I attempt to open a game. Removed because of that.