It would be a lot of fun to know what it stands for since you could make an argument they implied the El symbol was tied to the hope for a new beginning by its appearnace as a colonial flag and Jor-El extraterrestrial expertise. You can see some ancestor of that family (Ken-El) staying they look to the skies in hope and taking the symbol for their own. Maybe Zod's symbol is something like Duty?
And I loved the balance they gave to Zod's portrayal in terms of his presence versus Clark's story. He's nowhere near as background or hateable as most of the Marvel villains, but he's far more rational and unemphatic than the villains we saw in the Drak Knight Trilogy. Those guys were designed to drive the film from an emotional place in their souls, while Zod is still quite clearly focused on an obtainable and sane military objective. He may get angry, frustrated, and saddened by the heroes conflict with him, but he's psychologically focused on his mission and is really pragmatic about it. If he knew Clark had the codex, you know he would have killed him on the spot, not tried to deconstruct Clark's choices or torture him.