From (2006). Since then it's had 23 cites, mostly in the context of alternative medicine. The one study that seemed to investigate it[1] dismissed it in passing. The guy publishes a lot in Medical Hypotheses , on a wide range of topics (topical gallium for arthritis, taurine for cardiac arrythmia, magnesium for depression). The email address is at "coldcure.com". Which strikes me as having a whiff of crankery to it,…
Edit: coldcure.com was recently sold off but prior to that it had a long history of hocking naturpath "common cold cure" pills
https://web.archive.org/web/20060103011343/http://www.coldcu...
From a 1995 NYTimers article about the author George Elby
> MORE than 10 years ago, George A. Eby, a city planner turned self-educated pharmacologist, made headlines with a study showing that zinc lozenges could cut down the average length of a cold to about 4 days from nearly 11. [...] Although several studies have subsequently supported Mr. Eby's initial findings, others have found no such link between zinc and the common cold.
https://www.nytimes.com/1995/05/29/business/patents-751395.h...
I'd keep my bullshit meter slightly higher on this one.