Zn + O2 = ZnO
2Zn + O2 = 2ZnO
ZnO + 2HCl = ZnCl2 + H2O
ZnO + 2H+ = Zn2+ + H2O
ZnCl2 + 2NaOH = Zn(OH)2 + 2NaCl
Zn2+ + 2OH- = Zn(OH)2
Zn(OH)2 = ZnO + H2O