CHF 3.50 per person per night, including VAT. The source describes this as a voluntary accommodation levy (Citytax), not a legally mandated municipal or cantonal tourist tax in Zurich because it has no cantonal legislative basis. It applies to accommodation establishments affiliated with the Zurich Hoteliers Association or Gastro Zurich that have committed in their statutes to levy it; the source does not provide a separate Winterthur municipal rate or tiered adult rate.
Guests staying 31 or more consecutive nights are exempt from the Citytax starting with the 31st overnight stay. The source does not state other exemptions or reduced rates.
The source does not specify a separate Airbnb or short-term-rental rule. It says the Citytax generally applies to accommodation establishments that are affiliated with the named industry associations and have committed to levy it; whether a particular short-term rental is covered cannot be determined from the page.