Each protocol runs as its own separate network. You will have one Wi-Fi network, one zwave network, and one zigbee network. Devices of one protocol cannot repeat for the different protocol.
Each sub hub will act as a zigbee repeater and as a Z wave repeater for the network established by the primary hub, but that doesn’t give you any more range than just putting a light switch ( or any other repeating device) of that protocol in that same location.
So if there is a location which is out of zigbee range of the closest zigbee repeater, the zigbee radio in a sub hub that you put in that same location won’t be able to reach your zigbee network either, even if the Wi-Fi connection works fine.
The subhub might save you from having to buy an extra device to act as a repeater in that location, but it doesn’t suddenly give Zigbee or Z wave signals the ability to travel as far as Wi-Fi does.