You guys're forgetting the anime is reduced/limited to 4 moves now, right? Or are you just trying apply smogon/handheld physics to the anime? XD
Ash's charizard stands a forseeable chance vs Cynthia's Garchomp in all actuality. The moves her Garchomp has displayed are Brick Break, Giga Impact, and Outrage. Whereas Ash's charizard has are Flamethrower, Dragon Tail, and one or two other moves that actually escape me now (Seismic Toss is no longer a move...his Charizard is just good at grappling and throwing).
Could see the actual battle going like this:
Cynthia rushes in with Outrage, Charizard dodges and grabs it, spirals into the air, then tosses it down and connects into a Dragon Tail. That's going off the point where N had to stop Ash and Iris' battle though XD