It however only has moderate compatibility with ROM hacks made specifically for ZSNES. This was done as an April Fools day joke. In 2011, byuu released bZSNES - a modification of his bsnes that includes the optional inaccuracies of ZSNES and a similar GUI. However, because of the inaccuracies of the emulator, these tools and hacks are broken on other, more accurate emulators and real hardware. Many ROM hacks and ROM hacking tools were made using ZSNES as a testing platform because of its popularity. It is recommended to use Snes9x or RetroArch with the bsnes core(s) instead.

These are just a few problems, there are a few more listed here, and here. To get them to display properly in 1.51, you have to press 8 to switch to the old graphics engine, or just use an older version.

Transparency - Kirby's Dream Land 3, Mecarobot Golf, Jurassic Park and any game that uses pseudo hi-res translucency won't display correctly in the default graphics engine.

For example, Super FX for example is not clocked correctly - Star Fox runs twice as fast as it should.

Many of the co-processors, which are actually on the cartridges, are emulated in extremely strange ways.

Bad sound emulation - A ton of games sound terrible on ZSNES Earthworm Jim 2 has missing sound effects, some sound effects are missing or sound like short beeping noises, which is not correct behavior.

Snes9x vs Zsnes S-SMP emulation accuracies

Games crashing - Der Langrisser (freezes after 2-3 hours), Super Mario RPG (freezes in many different points of the game), Star Ocean and many other games have freezing and crashing issues.

Compatibility is lower than any modern emulator due to low accuracy to real SNES system.

SNES Pseudo Hi-Res translucency (Why you shouldn't use ZSNES!) The current 1.51 created more problems than it fixed and many problems still remain: The ZSNES developers focused on speed over accuracy, so a hefty amount of games have bugs (and some just plain crash).

Snes9x 1.51