so, TranZit & Green Run are the zombie maps. There are 2 Easter Eggs as hinted by the oddly named achievements. We already know that weapons & objects are create-able & upgrade-able. In TranZit, you don't need the power on to buy perks. The "Don't fire till you see" has to do with some sort of fire zombie or trap. Also, the "I don't think they exist" trophy has something to do with a jockey-type zombie (relating to L4D)