dmsbandit,
I don't know where you got your information on African game. While some kudu bulls get pretty big, on average they are not quite as large as big bull elk. They also do not have nearly the reputation for toughness as some other plains game animals.
Zebra size depends on the species, but the most commonly hunted species is also a little smaller than a big bull elk. They do have a reputation for being pretty tough, though my wife killed a big stallion pretty easily with one shot from a .308, using a 150-grain E-Tip, in the right place.
