What are the main differences between the zr2, ls and extreme....

as far as i can see the extreme has Body kit are there many more changes

 

ZR2 = lifted (2" stock body lift if I remember right). It also has bigger fender flares. It was the "offroad" type model, but it was all stock.

The LS is the standard Blazer. It was the everyday one you probably see the most of.

The Xtreme Blazers (and subsequent S10's) were lowered (not sure how much though) and came with the kick *** body kit you see on them. They were the sportier version of the Blazer.

Those are your basic differences. I'm sure someone can get into more details about other differences (mechanical wise) in the 3 Blazers.