This is always a judgement call, some people have sensitive scalps and others have bulletproof ones.
I'd suggest using nizoral 2-3 times a week, H&S 2-3 times a week, and I would use a non-medicated on the off days. I think the non-medicated would help prevent buildups, which medicated shampoos tend to leave on hair.
Again, this is very much a personal judgement call. Shampoos are really a matter for one to try and experiment with to find a mix that works for you and makes your hair feel good.