In most images from the Man of Steel set Michael Shannon is seen wearing a Mo-Cap suit. I have spoken with a very reliable source who is very close to Shannon.They have spoken to Shannon himself and learned why he is wearing a mo-cap suit. Shannon said that there was a suit of battle armor that Zod wears in the film. They tried to use a practical version of the armor but Shannon found it too cumbersome and was unable to move. So they are going to add it back in during post. I speculate that this is during a climatic part of the film, possibly before and during a big showdown?