From everything I've read, zinc picolinate is the form of zinc, that is one of the easiest for the human body to utilize,
so I look for that.
(Zinc oxide is cheaper, but overall zinc is not expensive anyway, and the mineral oxides are not as similar to food grade)
Some people take 15 mg a day, while some
(notably males , and also those who want help with sleep or with fighting infections)
often take double that daily dose.
Minerals are often helpful to take in evening, or in divided doses, but I havent read much that says that matters too much.