No, I was using my LT, which has a 12,700 GCWR. I didn't want to look up the ZR2's numbers, nor do I know what they typically weigh.Are you using a GCWR of 10,700 for your calculation?
Beyond that though, I'm also talking about vehicles other than the Colorado, which is why I mentioned the Subaru. And I mention that vehicle because someone on another forum was talking about towing a trailer slightly larger than mine with a Subaru Ascent because it has a 5,000 pound max tow rating. I haven't tried to find out what the other limits are on the Subaru, but I suspect that vehicle would be overweight on something or other.