The scientific study wasn't even for COVID-19 but another very similar Coronavirus and yes they said it would have no effect on the cells without ionization (specifically zinc entering the cell to blocking an RNA that's needed by the virus to replicate).

There was a video of a doctor breaking down the biochemistry of it that got posted here the last time Chloroquine came up, which I can't find just now.

If it were only just as easy as taking zinc pills... I take vitamins daily already just to be safe (there's far more than coronaviruses floating around). I just don't expect them to be enough to prevent something as serious as COVID-19. There's a reason Chloroquine is being studied and not zinc by itself and is 100x more expensive to buy on the internet than zinc supplements, even before it became a meme. It's just not that simple.

That hasn't stopped naturopathy from spreading before though.

Not in direct reply to your post, but slighty interesting anecdata: I likely caught COVID-19 1-2 days ago (light fever, headaches, loss of smell, but no runny nose): I gargled with Zinc as I noticed the first symptoms, had Cinchona bark tea yesterday. After a day, almost all symptoms disappeared except for the loss of smell, which is generally considered a late-stage symptom.

Given that the common cold without any treatment typically lasts around 5 days or so, it might point to some efficacy of the treatment.

Would you share your recipe for cinchona bark tea? How judge the strength and how much to drink per day?

I bought some cinchona bark (cut, but is powdery) and they have a recipe on the bag but no specification of strength or how much to drink.