Not to bump a 2 month old post, but people are still having trouble 2 years later getting the exact settings for this game. I was grateful to find this topic last night and finally got Zone 66 completely working with SoundBlaster audio, both music and sounds. I have to agree that the SB intro/main menu theme sounds much more fitting than the GUS intro.
Sax is right - this game is extremely picky when it comes to the SoundBlaster audio. You even need the right cpu core and cycles set for them to work, which doesn't really sound like it would make sense. I've reproduced the dosbox settings categories that I changed in the config file that finally allowed Zone 66 is work right. In a way, some of this is also a compilation of what other posters suggested to try, but all in one place for reference.
You need these CPU options set like this even if you have the right sound configuration, or SB music won't work.
The high rate is just so the music will be less scratchy when you get it going.
oplrate=49716 ............ To match with the mixer rate above.
Zone 66 says that it can detect SoundBlaster support if your irq is set to 3, 5, or 7. Personally I've found that setting games to 5 instead of 7 can help if you're having quality problems.
Stated by Zone 66 - xms needs to be off. Turn ems off to fix the extended memory complaint you get when running Z66 with xms false but ems true.
You could set a batch file to set the settings temporarily just for playing Zone 66 instead of using the config file, or just load these settings as a custom config file. After these are set, just run ZONE66.EXE without any force-sound switches - you shouldn't need them.