Chances are that the ZMA really isnt doing anything for you other than the placebo effect. The problem with it is that you can't take it within 2 hours of any calcium, and I guarantee that your protein shake has calcium in it. This affects the absorbtion, meaning you are probably not getting anything out of the ZMA other than expensive urine. I gave up on ZMA because there is no way that I can go to bed without some cassein in me, which provides about 90% of my daily calcium needs.