I'm going to guess the paper you signed to have the dealership service your car has some fine print on it somewhere stating they are not liable for any loss or damages to your vehicle while it's in their possession. That's probably why they're telling you it's not their problem.
If the car is totaled, Isn't your insurance company going to reimburse you the market value of the car?
To me it's no different than if someone stole the car from in front of your house and totaled it. Your insurance company should reimburse you the fair market value of the car and then go after the dealership's insurance to get their money back.
If the dealership had any decency, it would pay the difference between what your insurance reimburses and the cost of a new ZL1.
Like others have suggested, get yourself a good lawyer and be patient. This could take a while to settle.