I had a few lines written out about how bad of an idea this is, but I’ll try being nice about it.
First, you’ll need to post your current stats so we can help you out better. The fact that you’re 20 already sends up a red flag, as most people will consider you too young to be tweaking with your HPTA. If you’re worried about stuff being detrimental long term the longer you wait to use AAS (including prohormones), the less chance of damaging your HPTA.
Also, the fact that you think ZMA/tribulus/creatine is enough for a proper post cycle therapy means you don’t know much about AAS. It really is just a case of you not knowing what you don’t know. If you’re dead set on using, the best advice I can give you is to read the stickies, take some notes with a pen and pad, and read this forum daily for the next 6 months, then make your decision whether or not you still want to use AAS. If at the end of those 6 months you still want to use, you’ll be able to make a much more educated decision about how you’re going to go through with it.
Also, if you’re going to take notes, which I seriously recommend… don’t leave the pad out for mom and dad to find. Just sayin’.
For what it’s worth, this is all coming from a 21 year old.