John, I am very sorry you have to be dealing with this BS. It's clear the dealer is at fault and needs to give you a brand new ZL1 to replace yours.
I did some searching to find some similar stories and heres what came up. not sure if anyone has mentioned these, but they are all similar to your scenario, John.
An M5 wrecked by dealer technician on "test drive". Took 16 months to finally close the case.
A Porsche 996 wrecked by a dealer technician on a test drive
2005 corvette in for broken antenna and jammed trunk. Dealer drives, against the owners orders, and wrecks it. Car was eventually replaced with brand new 2007 corvette at no loss to the owner.
Hang in there John... we're pullin' for you.