Wow,that looks way easier than the one our coach has us do. We use four balls,four rackets and half the baseline and the service line. One ball at a time to the next racket until the balls are back at the start. It is a drill Pat Rafter used to use and we got it from a mate who used to train with him. It hurts like hell. Will try to get a video up in the next week or so.
Never give up.Never,never,never,never.