*Checks.* Oh, wait, can't one-shot Zeus. He's a lot stronger than the FR gods. But it deals, like, 900+ damage and can kill the vast majority of the FR gods.
Anyways, the trick involves stacking Arcane Thesis, Incantatrix, Practical Metamagic, and the like onto an Orb of Fire, reducing metamagic costs until you can pull off an empowered, maximized, twin, enervating, admixed, searing et cetera Orb of Fire for massive damage, possibly using metamagic storms to get the necessary metamagic feats.