Zigbee and Z-Wave are separate protocols...they don't interact.
So if you have Zigbee and Z-Wave devices, you need a good Zigbee mesh and a good Z-Wave mesh.
For smaller devices (contact sensors, motion sensors) Zigbee is preferred by some as it can be easier on the batteries used to power those smaller devices.
I have both types, most of my Zigbee are motion and contact sensors, plus I have some Zigbee plugs around the house to provide mains powered support for my Zigbee mesh. My Z-Wave devices are primarily switches and one or two wall plugs (also powered, obviously) and they create a strong Z-Wave mesh that my lock, garage door opener, water valve, and two or three Z-Wave contact sensors connect to.
Take a look at this thread, similar info to what you're asking about that includes other options that work with HE and don't use either Zigbee or Z-Wave. 
