Hi jhnjohnp. You purchased your 2016 MKZ in June with 43,000 miles on it. How much time and miles are left on your 4 year/50,000 mile Bumper to Bumper warranty? You are not happy with the ride and feel something is wrong, so why not make an appointment so any issues can be diagnosed and serviced before the warranty expires, instead of guessing what the dealer can and can't do or what their "response will be"?Hope somebody comes up with a fix. It's not the tires. The ride control is inconsistent. When it's working get an amazing stable ride, other times not so hot, and at it's worst intolerable in all modes, that is, comfort, normal, and sport. Discovered GM owners are having similar problems with their "MagneRide" to a point where they are disabling the system, and installing conventional struts/shocks. They sell after market kits for that purpose, but so far found no such option for Lincoln ride control. Haven't brought it to the dealer yet, but get the feeling their response will be, "Operating as designed".
It is entirely possible something was wrong with the car when you purchased it and the previous owner never addressed it either. Could be as simple as a broken or defective shock/shocks due to something that happened while the previous owner had the car.
Also, what PSI do you keep your tires inflated to?
Some additional advice: When you bring your MKZ in for service, do not just tell the Service Advisor what you don't like about the ride/handling, hand them the keys and leave. Instead, ask to have the Service Advisor or atech take a ride with you so you can demonstrate what you are feeling. If you can get them to feel it too, you've won half the battle of getting it properly diagnosed and corrected.
Let us know how you make out and good luck.