Hi Young, I hope you're doing well!
The KW21Z's ZigBee 3.0 Stack supports connection with devices from other manufacturers, as long as the other devices support the use of the ZigBee 3.0 Stack. Compatibility will depend on the functionality and implementation of the ZigBee stack on the other devices.
Since ZigBee 3.0 implements and collects the previously defined market-specific profiles, it should be backwards compatible with devices of this types, and be able to interoperate between devices.
Please let me know if you need some more specific information.
Best regards,
Sebastian