A couple of points:
1. They needed zinc. It doesn’t look like they used it. Big mistake if so.
2. My favorite theory of how HCQ works is that it protects red blood cells from being depleted of oxygen. So the patient recovers. There is no reason to expect a reduction in viral load. The medication doesn’t directly attack the virus.
3. The only really worrisome comment was about no visible difference in the apparent health of both groups. But the zinc could explain that.
Regarding your point 3, the late administration of the HCQ medicine (16-17 days after the display of the initial symptoms), was probably the main factor in the failure - but yes, not providing zinc did not help.
However, once you get to the point of organ failure (which they probably were at, or very near, after suffering through this disease for over two weeks), not much is going to work, unless God intervenes.
Zinc may be inhibiting the iron from damaged hemoglobin packets from competing with regular blood cells for oxygen much in the same way that zinc inhibits iron from rusting due to the galvanizing process.