Jackson's Z1600 is fully modulating. Most residential don't spend the bucks for that feature but certainly can be done. Best with 2 stage equipment.
What I was told when I asked was the following.
0. Carrier has the only infinitately adjustable damper zone system, the system automatically determines flow rates and static pressures. It also has a option available that allows for integration via IP as well as remote controls
1. Trane zone system is nice, but super expensive. It also requires dip switches to change air flow settings.
2. Honeywell only has fixed position dampers. I.E. 100% open, 50% etc.
I didn't get a good idea about the white rodgers stuff as it appeared to be very expensive.
I really like some of the features on the infinity system and it is going to take a lot to talk myself out of it. My real concern right now is that I have no good way to calibrate the price to see if it is reasonable.