This isn't good.
Also, which demigods die in the trojan war? IIRC Achilles isn't a demigod; only offspring of actual gods are, and Achilles was born by an immortal being (nymph) and a human, so is not in this category. Herakles was a demigod.
I am not aware of Zeus' plan in the trojan war; is it there in Homer's epic? (i know i should have read it by now... )