ZMA is a waste of money, yeah sure you can try it if you have some money to loose. It's only 30mg zinc asparate + 450mg magnesium asparate + 10mg vitamin B6! If you buy those supplements apart it will be much cheaper.
If you don't believe me you can read: Wilborn C.D., & al. Effects of zinc magnesium asparate (ZMA) supplementation on training adaptations and markers of anabolism and catabolisme. Journal of the International Society of Sports Nutrition. 2004; 1(2):12-20