In ZnBr2, the oxidation number of Zn is +2, and the oxidation number of each Br is -1. This can be determined by considering the overall charge of the compound. ZnBr2 is a neutral compound, so the sum of the oxidation numbers of the atoms in the compound must be zero. Since there are two Br atoms in the compound, each with an oxidation number of -1, the oxidation number of Zn must be +2 in order to balance the charges.