Is a zamboni a tractor

No, I would say not. Some of the early models of ice resurfacers were tracters that pulled a dump box to throw the snow into. But now the "Zamboni" (a name of a company and not actually what it is, an ice resurfacing machine) is a separate vehicle unto itself. Dictionary.com describes a tractor as a vehicle, often without a "body", used to pull other vehicles. Ice resurfacers of today don't need to pull anything because the box that snow is thrown into is incorporated into the vehicle.