The C6 ZR1 has maintained it
The C6 ZR1 has maintained it's value pretty well even in the wake of the C7 ZR1. The ZR1's specifically hold value because of their performance and rarity. The C7 ZR1 is even more rare than the C6 ZR1 was and even more powerful as well. With that said the C7 ZR1 will likely maintain a higher value than the rest of the C7 lineup when the C8 performance models make their appearance. There's a few reasons for this but it basically boils down to the C7 ZR1 being the last of the front engine Vettes, limited production, and it being the top dog performance model of the C7 lineup.