If you’re thinking of getting a Horizon treadmill that claims to connect with Zwift, be aware that while it is a very nice treadmill (mine’s a 7.4) that it does NOT transmit actual speed, only the speed value you have selected. When you change speeds your avatar immediately jumps to the new speed with no ramp. Also, if the TM is not accurately calibrated (mine is off a minor 0.1 mph) you will get an inaccurate speed on Zwift. Runn, on the other hand, transmits actual TM speed and your avatar will ramp up or down on speed changes.
While I think the 7.4 is an excellent performing TM, I was very disappointed that it does not transmit measured speed, and seeing my avatar jerk forward or suddenly halt in group workouts is annoying. I’ve moved back to using my reliable Runn. So much for getting a “smart” TM.