Carpenters often cut out the plywood sheathing from door and window openings with a reciprocating saw, circular saw or even a chainsaw. I prefer to use a carbide-tipped pilot bit mounted in my router. This type of bit has a sheathing cut outs point on its tip, so it can be plunged into the center of the work. Above the tip is a pilot bearing, which will follow the framing as the cutters make a quick, clean cut in the sheathing.
Michael Gornik, Nevada City, CA
