Use Smokescreen on it if your Charmander has it. If you get an Attract TM by roaming arond Mt.Blaze , that can also cheese the Moltres fight. I'd also set Treecko's AI to "Get Away" since Moltres can OHKO it, leading to an instant loss. Worst case scenario, you can also just grind using the last 3 floors of Mt.Blaze until you get strong enough to beat Moltres.