Earlier quoted context omitted.
Well if your loss of sense of smell went away after your first infection how can you say the zinc did nothing? You could say the zinc cured your sense of smell.
He could also say the peanut butter sandwiches he eats in the morning cured his sense of smell. I mean they probably didn't, but there's as much evidence either way.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7781367/
There have also been multiple reports linking the loss of taste or smell to zinc deficiency, either due to chemotherapy and metal chelating agents [38–40], or due to nutritional deficiencies, especially in older populations [41,42], also caused by medical procedures such as dialysis [43]. As a result, zinc has been proposed in the treatment of taste disorders [44,45]; however, zinc supplementation for chemotherapy-induced loss of smell or taste, which is often transient, has not led to improvements in this condition