Thriller Ant
Beep Bop Boop
Undertaker has wrestled in 30 minute matches before, plus his entrance is another 30 minutes so that counts as 60?
Sure Thez has more experience and can go the distance but you can't deny Undertaker's will to win in big match situations. If Undertaker were forced to be in an iron-man match, there is no denying he would be able to do it, it just so happens that he was one of the many wrestlers who didn't get to participate in one during his career. I don't think it matters as much as some users think it does. Triple H defeated The Rock in an Iron-man match but lost one to Chris Benoit, who never went 60 minutes before. Experience isn't a major factor, Undertaker never taps out and he rarely gets pinned clean. Undertaker also has more experience in brutal stipulations, which probably drain more out of the wrestler than an Iron-Man match would. I gotta go with the Deadman, he is more than capable of going over Thez.
Wrestling conditioning, both in and out of kayfabe, is all about cardio, so let's apply this to another form of cardio. 30 minutes, Undi's longest match, is obviously half of the length of this match, so let's take a marathon runner and a half marathon runner. If you put them up against each other in a marathon, somewhere between halfway and the finish, the half marathoner is going to run out of energy while the full marathoner can easily make it to the end. I don't doubt that Taker can get a fall or two early on, but when he gets gassed, Thesz can get enough falls to win with no problem.