I think there is a more important clue to Zod's purpose here. The container he is supposedly being carried in is labeled USAMRIID - United States Army Medical Research Institute for Infectious Diseases. While that is a mouthful and perhaps confusing, USAMRIID is the government body that works to counter biological weapons of mass destruction. This suggests that USAMRIID and Lexcorp have been working on a biological weapon, a virus most likely, to kill Superman. I believe the result is kryptonite (if you notice, the green rock in the trailer looked like it had been made in a lab). Regarding Zod, it is possible that he becomes a sort of Bizarro-like zombie, but I doubt they'll make him Doomsday.