4 NVH4ClO4-II 2 N20 + 5 O20 + 4 HCl + 6 H2O-II

This is an oxidation-reduction (redox) reaction:

4 NV + 20 e- 4 N0 (reduction)

10 O-II - 20 e- 10 O0 (oxidation)

Change the oxidation states