I have a 1998 ZR2 and noticed the other day that you can also look under your front wheel wells and their is a badge/stamp that will say ZR2 if its a real one. Just a quik and easy way to tell.
I agree though. That one looks wrong. See the tire size as well. All ZR2's came new with 31x10.50's. A regular blazer won't fit these without some sort of lift which you should be able to see. Most likely a body lift.

 

The original picture.
Could be a debadged zr2, again check the rpo codes is best
Flares look ok to me
My zr2 has the same rims as that
Only thing that does not look correct is the trim on the doors.

 

I bought my ZR2 brand new and it came with same wheels and no badging, minus the door trim.