@neildsbm No! Just no! That is wrong in everyway possible, and not supported in any bay in the Zigbee specification, Zigbee gateways, or by Zigbee Coordinator makers. The serial interface protocol on those Zigbee stack firmware not a bus, the serial connection is exclusive. Such a bad idea it borders on trolling trolling, especially when you bring this up in a thread that is specifically about stabilty.
You always need to use a separate dedicated Zigbee Coordinator for each Zigbee Gateway, period!
And as a wrote in the post above, using a network-attached Zigbee Coordinator adapter is a dirty workaround regardless that even when only using a single Zigbee Gateway should only be used as the exception in edge cases when it is not at all practically possible to just use a very long USB extension cable instead, epecially when you can simply convert any Ethernet-cable into a extremly long USB extension cable, see my Zigbee Coordinatoir adapter recommendations here → Zigbee buyer’s guide - #2 by Hedda.