The Technogym Myrun fits your needs, I accept Zwift isn’t built in but is designed to carry a tablet on the frame that effectively acts as it’s built in.
You could do this with any other treadmill in reality but the Myrun seems to be designed for this.
I will warm you though that trying to run whilst looking at Zwift on a small screen is quite difficult. Because of the constant motion of your head trying to read the text on screen is hard.
For this reason most people elect to cast from a tablet/phone to a TV.
You can save a whole heap of cash by purchasing a non smart treadmill which you can then use to purchase a dedicated PC or a tablet and a TV.
My setup is a non smart treadmill that cost £1000
PC - £80
TV - £50 (2ND hand)
QZ app.
It works seamlessly. Well it did until the treadmill died on Friday. Warranty replacement arriving soon.