I had 2 clawed frogs and 1 axolotl in the same tank. But when the axolotl got twice the size of the clawed frogs he became too big for the tank they where in, so then I putted him in the adult tank. I never had problems with this combination. When they are small it is possible but when they get big the axolotl will eat the clawed frog or if you have big clawed frogs, then they will try to eat the axolotl.
So keeping them separate is better.