Just like the MKZ (Mark Z) was formerly known as the Zephyr, the new MKX (Mark X) was formerly the Aviator.It's possible that the Z in MKZ refers to the Zephyr, and the X in MKX refers to the fact that the Aviator is a crossover SUV.Source(s):ust like the MKZ (Mark Z) was formerly known as the Zephyr, the new MKX (Mark X) was formerly the Aviator.