i have a ice weakness and rock weakness too.
Each Pokemon have their perks. I personally would say Zoroak has more perks, though I would not use it over Flygon as it is a very frail Pokemon. Flygon has nice all rounded stats and makes a great Scarfed and band users. Though if you have an Ice weakness and can fit Zoroak into your team, I would.
Chose Flygon if your team is weak to
Chose Zoroark if your team is weak to
If your team isn't weak to any of thoes types, then choose Zoroark.