FYI, there’s better forms of zinc than zinc sulfate ... here’s a pretty decent article comparing the different forms ... any fully-reacted chelated form is better than any inorganic form ... naturally, the chelated forms are impossible to buy right now, but it’s food for thought when manufacturers catch up:
also, too much zinc is indeed toxic ... best not to take more than 40mg of elemental zinc:
https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
If you want a form of zinc that is more readily uptaken by the mucous membranes, get some Cold-Eeze lozenges.
Take 30-50 mg zinc with 500 mg quercetin and a chaser of 4 oz tonic water that contains real quinine ( double these doses if you are symptomatic)
Poor man’s hydroxy prophylactic