The metal side of things goes in many directions. There was a whistleblower at a metal testing company who tried to raise the flag on testing standards issues that affected tests done on the metal from the twin towers.. He was sacked.
I've never heard of molten zinc causing a collapse - sounds unlikely to me, but I'm not a metallurgist!
There were allegedly molten iron spheres on the ground that were said to come from thermate (not thermite - different). I haven't seen enough evidence to know for sure, but it's difficult since the gov enacted the biggest cover up of a crime scene in human history during those days.. Shipping out an absurd amount of metal to China as I recall, without allowing any forensic work to take place.