If you want to shoot in servo w/ burst mode on a moving subject, single point AF, put it where you want the subject framed, and shoot.
Zone setting works great shooting birds in flight, with a clear background, it gives you more forgiveness in keeping on target, but with a busy background of an animal on land, the camera may focus on undesired parts of the "zone."
Single point expanded is a bit of a compromise between the two.
Really the 7D has so SO many focus modes you really just need to read the manual to make sure you have a fundamental understanding on what they do, and then get out there and use them and see what works for your subjects, settings, and style.