The humor in Zoolander ranges from dumb to tasteless, and there's pretty much no reason to watch it.
I wanted to see Zoolander when it came out - and I was 15 - but at some point I realized it wasn't worth seeing. I should've stuck with that. I'm not a huge fan of Ben Stiller, and the schtick he did for the movie didn't help. I do sometimes like Will Ferrell; he didn't have a huge part here, but he was good. Owen Wilson was probably the best part of the movie, but that didn't make it anywhere near worth watching.