N2H4 (aq) + O2 (g) → 2 NO (g) + 2 H2 (g)
This is an oxidation-reduction (redox) reaction:
4 HI + 4 e- → 4 H0 (reduction)
2 N-II - 8 e- → 2 NII (oxidation)
2 O0 + 4 e- → 2 O-II (reduction)
N2H4 is an oxidizing agent, N2H4 is a reducing agent, O2 is an oxidizing agent.