Yeah, there is one way i believe.
You’d wirenut the wires for your light and fan load directly to your line hot wire in the switchbox. Now the fan and light circuits are powered all the time and you have control with the zigbee fan/light controller.
Then you’d connect the z-wave switch to the hot wire and neutral wires, giving power to that switch but leaving it unconnected to any loads.
So now the switch can be seen by SmartThings, and you could create automations that when the switch is toggled, it could do something with your fan/light, or even something totally unrelated.
The question is, what additional functionality does this give you in your case?