Red Skull was okay in TFA, but nothing too special. I don't think there is much reason to think the writers have much more to offer with him.
Generally as a character I think he makes a pretty poor archnemesis. Cap is an idealist, and there's little challenge for him to find in a character who is a monstrous Nazi. A monstrous Nazi works really well for an old fashioned WWI adventure film, but with the more ambiguous direction the franchise is going on, I say let his fate be one of those mysteries that never gets an answer.
I don't know a lot about Zemo, but I think his story bears much similarity to the main conflict in Iron Man 2, so...
Zola returning would be overkill, I think.
As unhelpful as it sounds, my choice is 'whoever can offer Steve an interesting challenge'.
A couple of years ago, I think precisely zero people would say 'Alexander Pierce'. Yet, he's Marvel's best villain so far IMHO. I wouldn't be opposed to the writers making up their own villain and slapping on the name of an existing minor character like, I don't know, Anna Kapplebaum.
But my own preference would be Madam Hydra, assuming Marvel shares the rights with Fox.