If you can get your hands on identical-state saves for the two emulators (saves made at the same point in the game with the same saved content, e.g. perhaps the very first point in the game you can save) and account for the un-gzipping as needed, you may be able to eyeball the two saves side by side in a hex editor and spot where a recognizable chunk of bytecode starts in each. The structure of the file will likely be an emulator-specific header (which may even be nominally human-readable) followed by some possible padding bytes followed by banks of game memory, likely in easily-Genesis-addressable-sized chunks. I'm not certain architecturally what addresses on Genesis are writeable, or whether different games used different or unusual banking or addressing hacks, so it may be more convoluted, but that would be a starting point. You may even want to look at multiple uncompressed savestates from multiple games to see whether you can work out how big the headers are, since they're probably a fixed size for all files. Once you know what the offset is between where data is in the two savestate formats, ~hopefully~ the layout of the save data itself is consistent and identical to the layout in Genesis memory, meaning you can just offset the addresses given in the instructions and edit those bytes in the Mac save.
