A latching relay, also called impulse, bistable, keep, or stay relay, or simply latch, maintains either contact position indefinitely without power applied to the coil (wiki). In the electronics world, these relays have two contacts to open and close the switch.
You should define the ON pin first. For example, output 7 – Bistable relay ON, and output 8 – Bistable relay OFF.
Zigbee: Look for commands and examples for GPIO outputs. The firmware accepts all commands on the “Bistable relay On” endpoint.