Which reaction does not occur in roasting process.

On roasting $\mathrm{H}\mathrm{g}\mathrm{S}$ and $\mathrm{P}\mathrm{b}\mathrm{S}$ sulphides ores are partly converted into their respective oxides. Since the oxides of $\mathrm{H}\mathrm{g}$ and $\mathrm{P}\mathrm{b}$ are unstable. While that of zinc is stable, therefore, oxides of $\mathrm{H}\mathrm{g}$ and $\mathrm{P}\mathrm{b}$ bring about the reduction of their sulphides to metals, but zinc oxides does not reduce $\mathrm{Z}\mathrm{n}\mathrm{S}$ to $\mathrm{Z}\mathrm{n}$ metal