2 H2PIVO3 + 7 Zn0 + 14 HCl 2 P-IIIH3 + 7 ZnIICl2 + 6 H2O

This is an oxidation-reduction (redox) reaction:

2 PIV + 14 e- 2 P-III (reduction)

7 Zn0 - 14 e- 7 ZnII (oxidation)

H2PO3 is an oxidizing agent, Zn is a reducing agent.