Hi Nick,

it should be the Gemeinde. As in Albisrieden the Gemeinde and the Policestation are just 1min from each other that shouldn't be a problem.

It will be tough to get a permission in the City of Zürich as it is normally just allowed August 1st and New Year. More chances if you have just Volcanos and sparkling thingis which don't make much noise.

Bonfire shouldn't really be a problem, there are plenty of public fireplaces around.