The old z71 was what the new Trail Boss is now. Over time, GM lowered the front end and added that *REDICULOUS* chin strap under the front bumper - even on the Z71. And they made the front skid plate plastic. AT4 is nothing more than a GMC branding of essentially the Z71.Actually I believe the new 2021 Tahoe Z71 and Yukon AT4 are essentially the Trail Boss versions of the SUVs
As a matter of fact, the Trail Boss is built up off of the current Z71
My Z71 GMC Sierra came with the front end way too low for my taste, and with that chin strap. Both of which I plan to change. So Z71 is not now the quality it used to be