Not all that far adrift from the original, for me.
I would class 'Zoolander 2' as a step below its predecessor, but there's not much between them in my opinion - admittedly, I only found the first film to be marginally passable. It starts off well, I was liking the opening few scenes. That interest of mine definitely waned as the run time went by, though there's still enough there to avoid proper boredom.
Ben Stiller, Owen Wilson, Will Ferrell and Penélope Cruz make the film watchable enough. Cyrus Arnold does alright as the kid, while the numerous cameos are minorly amusing to see. I can't say it's a film I enjoyed or that I'd rewatch, but I didn't find it be all that bad either.