Did you actually understand how the stat is calculated?
It's a function of the percentage shot at rim by player opponents and the percentage of shots contested. Zeller gives up a relatively high percentage at rim, but contest a lot of shots, hence the high amount of points prevented. That's the equivalent of a volume shooter and not exactly a glowing endorsement of his defenaive prowess.
It's nowhere near that simple.
This is one instance where statistics fall a little bit short of giving you the full picture. What you need to decide for yourself, after looking at the data, is whether his high contest % is a product of the system that he's playing in or if it's because he reads the play well, uses his feet to get to the right spots, doesn't bite on pump fakes, etc.
For example, Serge Ibaka's ranking is seriously deflated here, because he's a PF. A lot of the time he's not in a position to contest a shot, because the system has him guarding a stretch four on the perimeter. But if you put him in at center and ask him to just patrol the paint for 24 seconds, his contest % would probably rise to around the 50% mark without much loss of efficiency, which would put him in the top 5.
On the other hand, a guy like Dwight Howard lives in the paint and yet he's still only contesting 42.1% of possible shots at the rim, according to this data. This is very interesting, and may go some way towards challenging the widespread belief that he's an elite rim protector. Sure, he's effective when he contests a shot, but what good is that if he's not getting himself in the right places to contest the shot in the first place.
I'm not an expert on big man defensive positioning, so hopefully someone else can do an analysis of why Zeller's contest % is so high. Maybe then we can decide if this data means he's an elite rim protector or just an average one.