How do I cut a hole through vinyl siding?
Cutting the vinyl siding is easy. A hole saw, tin snips, etc, will slice right through it. When we cut with a circular saw, we often install the blade backwards to minimize ripping and tearing of the vinyl. That said, the hole is the least of your effort. You need to be sure the weather stripping and siding itself is properly done to keep the siding water tight. See this answer for a full description of how to handle the tyvek, installing J-channel around the opening, and remove/reinstall the siding. One important consideration is that vinyl siding expands and contracts, so you don't want to make a fixed hole that fixes the siding to the house, otherwise you'll risk warping and buckling.