Yep, why would you want to though ? Remeber although there is no set limit, everyone has a limit to how much protein they can take into their body at anyone serving.....
I'm down to about 2 lbs. of each. rather then alternate my servings between each, I thought I'd mix them. Since the Nitro-tec has more to it and the gnc is pure whey, I figured mixing them together would give me steadier equel suppliment dose per serving.
To save yourself money, you might be better off drinking the fast acting whey as you would normally after a workout, and then waiting to give it time to just trickle into the muscles....say about 50mins, then have a high carb and medium protein with little to no fat meal. The protein in this meal can be your longer digesting mix.... just another idea.