Highlights is highlights and they always can make a player look good.
Nevertheless, my favorite bit from the Zeller vid is near the beginning, when he simply pushes Drummond through the post in order to gain the advantage for the rebound. That was probably a foul, but it is indicative that Zeller is stronger than he looks.
He played a lot better later in the year last season, probably a combination of getting further removed from the emergency appendectomy in October and simply getting more significant minutes.
I think that if he has a good summer program and can pack the muscle mass back on that he lost plus maybe a wee bit more, he could be at minimum a significant improvement at the C position over what we had last year. And I think he still has decent upside. Big men tend to take several years to mature in this league.
He's not likely to be the next Wilt Chamberlain. But I think Zeller will prove to be a very decent, solid starting center in this league.