well i always subscribed to the theory that the brain could still be alive even if you cut the head off, but as for its movement capability after an accident like that it would depend on the damage anything from partial paralyses to it becoming a paraplegic, to full body paralyses. remember a zombie is nothing more then the walking remains of a human, the empty vessel left over after the spark of life is extinguished. its just being manipulated by an outside force, like a puppet having its stings pulled. but its still limited by human physiology. so to answer you question that same thing that would happen if a human injured their neck. only difference is a zombie will keep trying to continue on as long as it can. like if it loss the use of its legs it would try to crawl after you.
that is of course if were talking about the undead kind, with the living kind would be exactly like if a person took that fall, they would probably die form it. either from the initial injury, or trying to continue on, since they too will always try to come after you as long as they can. meaning they would probably make it worse, or they may jsut become stuck there and die from exposure.
But we would then suppose that they can be immobilized , short of destroying the actual brain.
yes that's always been my assumption, my plan for dealing with them in a melee situation is to let them get close then circle around behind them and strike the back of the neck where the spine attaches to the base of the skull. if you have an edged weapon it will sever the spinal cord essentially locking them in and making them useless. with a blunt object you will almost certainly bark the spine resulting in the same immobilization.