A boring 1 trick pony. Not a real actor or comedian.
He plays the same character in everything he does. Yes, I have seen a -lot- of his work. I used to enjoy him until I continued to see him doing the same thing over and over and over. He has no acting talent what-so-ever. There is being type-cast then there's being 1 dimensional. Zach has 0.5 dimensions on a good day.
What I have seen him do:
Bubble Boy
The Hangover
Just 3 Boyz
Tim and Eric Awesome Show, Great Job!
Dinner for Schmucks
It's Kind of a Funny Story
Due Date
The Hangover Part II
Tim and Eric's Billion Dollar Movie
The Campaign
The Hangover Part III
Are You Here
Birdman
Also not sure chronologically where Between Two Ferns fits in but add that to the list.
For some reason his popularity is only increasing too.