Most viruses: specifically the ones that use an RNA-based method of reproducing. Some viruses use a DNA-based method (Herpes was mentioned as an example). The presence of Zinc(II) ions inhibits the action of proteins necessary to replicating RNA, and HCQ causes the cell to close down some of the exit portals that allow Zinc ions to leave the cell. Azithromycin, on the other hand, is a potent antibiotic that's effective against many bacterial infections that can cause pneumonia, sinusitis, etc. and thus it can help a lot to clear up opportunistic bacterial infections that frequently accompany COVID infections.