Horses returning to the Champion for another crack do have a good record, so you may have a point with Zarkandar but he just never struck as an obvious CH horse. He did run on very strongly when it was all over in the Champion, but was slightly off the bridle at Aintree over 2m4f before coming down.
My thought was that he was rushed back. Winning the Betfair was impressive, but in any normal case surely he would have been given a bit of time off afterwards. The festival was round the corner though, which would have taken a lot out of him, and come Aintree I think he was running on empty. I think coming in fresh this season we could see a completely different horse.