The sulphate ion has a -2 charge
Zn(s)+ CuSO4(aq) -+ ZnSO4(aq) + Cu(s)
In the above equation Zinc is (oxidized / reduced) while Copper is (oxidized / reduced)
In the given equation:
Zn(s) + CuSO4(aq) -> ZnSO4(aq) + Cu(s)
Zinc (Zn) is oxidized because it goes from an elemental state (Zn(s)) to an ion state (Zn2+(aq)).
Copper (Cu) is reduced because it goes from an ion state (Cu2+(aq)) to an elemental state (Cu(s)).