You can get zinc vapor by reduction of oxide with carbon powder at around 1 100 ºC. You have to collect it in a non-oxidizing recipient (a retort) to allow condensation in liquid form without oxidation. I find, however, it will be more practical to leach with sulphuric acid, purify and then obtain zinc by electrolysis. But this will depend on the composition of the dross. If it contains Cl, probably not the best option.