Which method is used for the commercial refining of zinc?

Carbon reduction

Metals less reactive than carbon can be extracted from their ores by reduction.

Zinc oxide, ZnO, reacts with carbon at very high temperatures to form molten zinc and carbon monoxide.

This is also a displacement reaction, and occurs because carbon is more reactive than zinc.

The more reactive carbon displaces the zinc atom, causing the zinc–oxygen bond to break while a new carbon-oxygen bond forms.