2 H21/2Cl + Zn0 ZnIICl2 + 2 H20

This is an oxidation-reduction (redox) reaction:

Zn0 - 2 e- ZnII (oxidation)

4 H1/2 + 2 e- 4 H0 (reduction)

Zn is a reducing agent, H2Cl is an oxidizing agent.