Does it work?

Multiple studies in developing countries found that zinc supplementation may reduce the severity and duration of diarrhoea in children, especially those that are malnourished and with low zinc levels. Additionally, the healing process of gastric ulcers may be enhanced through treatment with zinc, although further studies will be needed to determine to what extent zinc may be beneficial for patients with this condition.

Dangers and possible side effects....

Zinc is generally considered safe when taken at the recommended dosages. Avoid zinc chloride since studies have not been done on its safety or effectiveness. Avoid with kidney disease. Use cautiously if pregnant or breastfeeding. Side-effects includeabdominal pain, nausea, headache.

References:

https://www.evidence.nhs.uk/formulary/bnf/current/9-nutrition-and-blood/95-minerals/954-zinc