Reading your post, you almost imply that one would sneak zinc into the collection cup.
That because youve mentioned zinc as an "adulterant". When you spike a urine sample with an agent thats known to destroy drug metabolites, thats referred to as adulteration in the eyes of the DHHS.

According to the article in your first link, the ingesting of zinc interferes with the function of the ELISA Immunoassay, in much the same way aspirin used to interfer with the function of the first-generation EMIT screen. Theres no evidence that zinc has any effect on THC metabolites in ones body.