there seems to be so much hate for the destruction in this movie yet while reading comics no one gives a crap about that and casualties.
in Smallville(the show) clark never moved anything anywhere when he fought zod there,zod(in lex's body tackled clark into an empty field) and any of the other fights it was very convenient how they all took place in deserted areas.
Anyway-the other Kryptonians didnt care about his mom they only cared about retrieving clarks ship. Zod was the only one to grab her then when she told him off she was flung aside.
if he took out the world engine in metropolis he would have damaged the phantom drive,therefore having no way to send the kryptonians who would all become empowered back to the phantom zone. Hence, Earth would be royally screwed.
Zod (and the other kryptonians) didnt giv him the chance to to protect all the people in harms way,if he ignored Zod and the immediate danger to help everyone,your right it would have been a very different movie,there would be even more destruction than there already was and Superman would be killed along with the rest of the people on the planet.