The Zimmer score is almost nonexistent. (Interestingly the soundtrack release has been encoded with DTS X, a 11 channel surround system designed for regular 2 channel headphone usage.)
And if you simply dropped in the original Williams score, as great as it is...it wouldn't have any real effect.
You know, it wouldn't have been that difficult to have a plot that questioned the idea of Superman in a modern context, while still actually maintaining a sense of both the character and escapist fantasy. But that's a huge no-no in Nolan-world.
Although being heavily shortened, the best "Superman" feeling I've gotten in the recent past was the DCAU dtv release Superman Vs. The Elite. That's a Superman story!