6 Zn + 4 H2SO4 → 3 Zn2SO4 + S + 4 H2O
This is an oxidation-reduction (redox) reaction:
SVI + 6 e- → S0 (reduction)
3 SVI + 6 e- → 3 SIV (reduction)
6 Zn0 - 12 e- → 6 ZnII (oxidation)
H2SO4 is an oxidizing agent, H2SO4 is an oxidizing agent, Zn is a reducing agent.