That would imply that red meat eaters would be less likely to get cancer which doesn't seem to be the case. I'm not saying that zinc isn't a factor, but I think that saying a blanket "Zinc is needed to prevent cancer" is irresponsible. We should be so lucky that we can narrow it down to a single dietary element or be able to blame it simply upon nutrition.

That’s not how statistical implication works… Learn about sufficient condition vs required condition before you start criticizing people. Taking zinc and smoking cigarettes still increases your chances of cancer, for example.