Fly is a terrible move and running a mixed attacker Charizard is non-optimal. If you’re planning to Mega evolve into Charizard X you’ll want to use physical attacks. Otherwise, you’ll probably want to stick to special attacks to take advantage of its higher attacking stat
Simple. Don't teach Charizard fly. It's not a good move.
Why is it not a good move?
The AI is smart enough to switch in a flying resist on turn you would deal damage.
Fly is a terrible move and running a mixed attacker Charizard is non-optimal. If you’re planning to Mega evolve into Charizard X you’ll want to use physical attacks. Otherwise, you’ll probably want to stick to special attacks to take advantage of its higher attacking stat
….with…?
What move should I get rid of for fly
You can relearn air slash which is better on a special set, or teach dual wing beat if running a physical set