If a Zen mode Darmanitan healed itself by potion, Heal Pulse, ect, then would it switch back to normal mode? Just wondering since I don't have one with Zen mode.
When Darmanitan's HP drops to below half, it will change into its Zen Mode at the end of the turn, which is a dual-type Fire/Psychic form. If it loses its Ability, or recovers HP to above half while in its Zen Mode, it will change back to its Standard Mode. Darmanitan will revert back to Standard Mode outside of battle and enters battle in Standard Mode, even if its HP is below half.
Source.
It reverts back to normal form right after it's health goes above 50% again.
Hope I helped!