Zipper merging is one of the dumbest things ever. Why? Because it assumes that nearly every single driver is a good driver and thinks logically while doing so. As anyone who drives may know a lot of idiots are driving cars. You couldn't get 5 cars into a zipper without honking, swearing, fingers, or people cutting each other off blocking it. It does not work in reality. It also assumes everyone is on the same page, leaves ample room between cars, and most importantly...minimal lane changing and fairly consistent speeds across the board. Which I would say none of the above ever happens.