what is the Z71
The off road package.
Z71 is a package code. You will find that code in the glove box of your truck on a sticker with all the option codes on your vehicle. Z71, as F_O_R states, is a off road package. It has skid plates on your main components and Rancho shock absorbers. If its not on the sticker, its proably a fake.
Like the other guy said, skid plates ,heavy duty shocks,heavy duty trans coller. Hope this helps, people love them z71 s and they usually bring more money