Mr(ZnSO4) = 65 + 32 +16*4 = 161
W(Zn) = Ar(Zn)*n / Mr(ZnSO4) *100% = 65 * 1 / 161 *100% = 40%
W(S) = Ar(S) *n / Mr(ZnSO4) *100% = 32 *1 / 161 *100% = 20%
W(O) = Ar(O) * n / Mr(ZnSO4) *100% = 16 *4 / 161 *100% = 40%