The Scenario
Greater Sci-Fi combatant
While it is irrelevant to the conversation, I would just like to say that if Link was immune to Zant's crystal with the Master Sword, he would be unable to change forms at all. The process goes: Link touches it, changes, does whatever as a wolf, then changes back at will. The dark fog does the same thing, but only as long as Link is touching it; once he leaves he's free to change. So it seems that effects only work if they are constantly in effect, as if they are instant,the moment the pressure's off, Link can go back. BUT, there's a problem there. Link can stand, untransformed, in the Twilight Realm itself. It could be that the Twilight Realm's effect wasn't enough until the dark fog was introduced, which is possible since Zant's crystal was a more concentrated and solidified version of the dark fog. There's also the Fused Shadows and Mirror Shard to consider, as Link resisted their effects as well. I would say Link has passive resistence to average transformation effects, and active resistence to stronger effects that get past that resistance and are instant. The only thing Link has trouble with, then, is a powerful effect that gets past normal restistence, and is also a constant effect that does not lessen, or else Link could remove it.
I wonder if the Triforce of Courage would remove any transformation effects and just turn Link into a wolf regardless of the intention...?