I used all 3 at the same time.
I usually use ZMA + few grams GABA,when I was using the old PowerFULL I took 2-3 caps of that with the ZMA and GABA.
Sleep was very good but waking up was harder and I felt groggy in the morning.
I would say use ZMA and GABA or ZMA and PowerFULL and switch depending on what you are using at the time.3 is over kill in my opinion but it does'nt hurt to try for yourself I think.