If your calf and/or feet are going numb, then they’re too tight. You can have a bit of difficulty zipping them up at first, but a couple of days of wearing them, or spraying them with alcohol should take care of the problem.
Wearing boots that are too tight can seriously compromise the zipper or zipper stitching in a relatively short period of time. If you can afford expensive boot repair and having your boots in the repair shop for several weeks to a month, go for it.