The Jim Lee/Brian Azzarello Zod was the Kryptonian version, or at least was originally intended to be, but unfortunately fan reaction to For Tomorrow was so mixed due to how bizarre the story was that they opted to retcon the whole thing and say that wasn't the real Zod, but rather a construct of the Phantom Zone or some bullsh**.
There were interviews before the series where someone (can't remember if it was Azzarello or one of the DC execs) said that they would be re-introducing a classic villain into the series and he would be a top-tier villain once they were through. They were clearly referring to Zod (although they didn't say so at the time because his appearance at the end was meant to be a surprise) but then after the series was over, they not only dropped the Zod story but I believe acted as though the whole thing never happened in the first place.
Kind of a shame, really. As I was reading For Tomorrow, month to month, all I could think was "WTF is going on in this story?!!" but once I was able to go back and re-read the whole thing in its entirety, I really thought it was quite good.
But for whatever reason, at that period of time, DC was doing a lot of strange things, apparently teasing fans with ideas and then yanking the rug out from underneath them (particularly whenever Jim Lee was involved). The whole Hush debacle still leaves a bad taste in my mouth. I still maintain that the entire point of Hush was to bring Jason Todd back, but the fans figured it out beforehand and thus they changed their minds and just made the red herring character turn out to be Hush instead. Which was stupid considering they brought Jason back anyway and then RETCONNED his brief appearance in Hush to say that it WAS the real Jason and not Clayface.
Of course, if you haven't read that arc (don't... it's a waste of time and money) you probably have no idea what I'm talking about.