It's possible that Zod, Faora, Jor-El and others' armors behave dynamically with several moving parts, including presumably a retractable helmet. I'm reminded of the scene in Prometheus when the Engineer suited up in his "space jockey" chair:
http://www.youtube.com/watch?annotat...&v=StBMEpWreGk
Perhaps, Zod & co armors have similar concept.