I have one of the Zercoms, but it might take me awhile to find the instructions, packed away in my last move no doubt. I use a Vex FL 18 right now. The Zercom is a great unit though. If you've ever used a flasher, then they pretty much work the same way the ones today do, except without the zoom features. What questions in particular do you have?
If I can find my old user manual then I will try and scan it in...if I can find it!