hmm... i forgot to mention how the sound files work... my bad. Zoo tycoon will only play sound files if they are .wav format and are inside the zoo tycoon folder somewhere. So you have to put the .wav files somewhere in the zoo tycoon folder. (I made a folder called sounds in my zoo tycoon folder and put them in there). Then use zookinii to change the theme song to one of those files.
Also if you need some good wav files to use for testing out the mainmenu theme song, here is a zip file with all 5 of the theme songs from ZT2 and the expansions.
https://drive.google.com/open?id=16xE0eZY6Mjxkq47FwLFtvNm6ZdszjhyU
I'm sorry I forgot to mention this in the instructions above, I hope you didn't waste too much time trying to get it to work. Sorry!