EDIT:
I guess a better way to word this would be that the single lion goes toward the center zebra of 3 that are closest together, angle-wise. No matter how the zebras are set up, at least 3 zebras must be adjacent and separated by angles of 3.6 degrees or less. One zebra could be on the opposite side of the lions from the other zebras, in which case the lion would go for a zebra that has the least sum of angles between itself and the two adjacent zebras. If the zebras were separated by 3.6 degrees each, then this would be the optimal strategy for them, however they would still lose. They wouldn't lose if this angle is greater than or equal to 90 degrees, because no matter how far out the lion goes, it's distance to cut off any zebra will always be longer than the distance the zebra must go to get to that same point, so it will never catch any of the zebras. For any angle less than 90 degrees between each zebra, the lion can get to a point far enough away from the circle that it will be able to "cut off" one of the adjacent zebras to the one it was following. If the adjacent zebra that the lion targets decides to cut over, it will be cutting into the path of another one of the zebras, and if two of these zebras are in the same path, then it will be simple for a lion to get one of them because the lion can move 200m for each 100m moved by each zebra.