" A Zebra that decides to try to scare off the Lion, but isn't backed up by the rest of the herd, or isn't backed up by enough of them quickly enough, is dead meat. "

Not necessarily true. An injury by a kick is a huge problem for the predator so they often shy away if the animal fights back. I have seen plenty of videos where single zebras or deer chased a predator away. Obviously this changes if there are several predators.