Zeke was truly great for a couple of seasons -- seasons where they used him a lot. He then held out to get his mega extension earlier than any other RB. From the moment his new deal was signed, his play declined. Even when showing signs of decline, they kept over using him because he was a great pass blocker. The milage on Zeke is so high because he was taking a beating even when he wasn't getting touches.
Zeke is also a sign of why you don't draft a RB with a top five pick. It's very rare for a RB to remain productive for years, especially when you draft one that high and feel the need to over work them because they're so great.