The melting point of Zinc is indeed 420 degrees, but Celsius not Fahrenheit. I am not sure that my stove top can reach those temperatures. You are right about it being toxic, I'll keep that in mind if I leave the country and make gun metal.
The article was from apparently 1992, before the twin tower attack. Of course it wasn't geared towards proving or suggesting the cause of the collapse of the twin towers, but showing that the phenomena of liquid metal embrittlement of molten zinc on steel was already documented and didn't need my repeating. You chose to focus too far into one specific example, instead of as general concept.
A36 steel is one of the types of steel that was used in the world trade center. Galvenized steel can include A36 steel like seen in the above article, but galvanization makes structural steel weaker. There are standards that try to minimize LME during the galvanization process but it can still occur. Supposing that sufficient molton zinc (or even lead, or some other metals) came into contact during the impact then the fuel combustion would make the temperatures by ripe for the LME but there would be substantial additional stress if not from the impact then from the structure itself enhancing LME potential.
I should have immediately pointed out that I am not a metallurgist, and have no specific expertise based on experience. What is in the papers you are providing is my source on these issues, except for my lifelong experience with galvanized pipe, which isn't very brittle as a rule.
I very much appreciate your pointing out the noob error of confusing Celsius with Fahrenheit.
The steel in the Twin Towers was not galvanized. Even if the planes were made of solid zinc, they would not have so embrittled the towers as to cause collapse, because almost all of the heat from the explosions of the fuel was expended in less than one minute. There was no zinc to embrittle the steel,and the towers didn't collapse immediately, but only after significant time had passed, revealing that sudden embrittlement did not contribute to the collapse.
Absent thermite and thermate, and intentional demolition, the towers would not have collapsed. LME was not a significant factor in that demolition. In this last paper you have provided, steels beyond stainless are revealed to potentially be subject to LME. Regardless, unless you propose some mechanism by which the planes coated the internal structures of the towers in liquid zinc, and caused it to penetrate deeply into the 24" thick supporting members, LME could have played no part in the demolition of the towers on 9/11.
LME is a highly localized phenomenon, and restricted to the surface of even sheet steel used throughout this paper. Such surficial effects would have had almost no effect on beams 24" thick.