Two products can both be described as smart and still have very different needs. One might communicate with a local hub, while another depends on a service outside your home. Before expanding a setup, draw the route from the physical device to the control you use.
That sketch exposes useful questions. Which part needs internet access? What happens when the hub is unavailable? Can you still use the device by hand?
Understand the role of a hub
Home Assistant’s ZHA integration connects compatible Zigbee devices through a supported coordinator. Zigbee networks use different device roles, so it helps to understand which products can extend a network and which depend on other devices for their connection.
Read the documentation for the coordinator and integration you plan to use. Check the exact device model rather than assuming that every function will be available because a product uses Zigbee.
Record what depends on what
A short inventory can include a device’s room, communication method, integration, and manual fallback. Add a note whenever you change a hub or move a device. This is useful when a routine stops working and you need to find the broken link.
See the official ZHA documentation for compatibility, network concepts, and troubleshooting guidance.