Lots of places sell zinc to the general public. It’s not considered dangerous.
Zinc is pretty harmless on its own, and it is not D.O.T regulated.
The amount of zinc used in the lab for N-Oxide reduction is extremely small. No one will care if you buy zinc unless you buy tons of it.
Unless there’s a way I never heard of, to convert pretty much any form of zinc back into pure zinc requires huge amounts of heat. You're not going to be able to do it at home in the oven.
The heat needed to convert zinc oxide back into pure zinc is 1975 °C (3587 F).
You may remember me as 69Ron. I was suspended years ago for selling bunk products under false pretenses. I try to sneak back from time to time under different names, but unfortunately, the moderators of the DMT-Nexus are infinitely smarter than I am.
If you see me at the waterpark, please say hello. I'll be the delusional 50 something in the American flag Speedo, oiling up his monster guns while responding to imaginary requests for selfies from invisible teenage girls.