If your goal is to control zigbee bulbs with a smart switch, the best solution would be to use the Blue Series dimmers when they come out (current estimated release in September)
You could probably accomplish something similar with the Red Series zwave dimmers, but it will heavily rely on automations to interpret scene commands. I think the biggest challenge would be getting dimming to work the way you want it. If you want to hold the buttons down to gradually dim the bulbs, you would need to figure out a way to tell your bulbs to start dimming when the button is held down, and then to stop dimming when the button is released. I dont have any zigbee devices so I dont know if it is possible (its not even easy to do with zwave). You might be able to write a loop of some sort that sends a bunch of commands to incrementally lower the brightness as long as you hold the button down, but it will never work as efficiently as a dimmer that natively supports zigbee.