Zip files are almost never required or of any real help. This is especially true for cart based systems where the ROM files are already extremely small. Zipping them just adds more process overhead before you can use the file. If the emulator has to unzip before reading the file it can also wear out SSDs because you have to write to the disk so much more often. CD based systems all have compressed file types that don't require the entire file be uncompressed to read and should be used to save space. Extensions like CHD, RVZ, CISO, etc.