Configuration of 'a/b/c/d' topic-path for external MQTT-broker instead of 'homeassistant' 'zigbee2mqtt'

Description of the issue

Currently MQTT-Messages are sent to my external MQTT-Broker from Homeassistant-Server to a topic path 'a/b/c/d'. These messages end up to be at 'homeassistant' and 'zigbee2mqtt' as so are at topic-level 'a' (root-level). I would like to have the following topic paths: 'homeassistant' -> 'a/b/c/d' -> So no 'homeassistant' in the topic-path 'zigbee2mqtt' -> 'a/b/c/d/zigbee2mqtt'

According to the documentation I can configure 'base_topic' but that appeared not to work with 'a/b/c/d', even using a/b/c/d/zigbee2mqtt, and this is only for the messages for zigbee2mqtt itself. The topic-path 'homeassistant' as stated I want to be replaced with 'a/b/c/d' or to be at 'a/b/c/d/homeassistant' but I do not see any option for that in the documentation.

PS: I would rather have the messages to be the Local Broker, but since I can only setup one MQTT-Client at the same time in Homeassistant, the messages have to end up at one MQTT-Broker, at least that is how I understand it now. So they should have the same 'Discovery prefix' My question is, how can I change these paths to obtain my desired setup?

Addon version

v1.33.1-1

Platform

Home Assistant 2023.10.5 Supervisor 2023.10.1 Operating System 11.1 Frontend 20231005.0

Logs of the issue (if applicable)

No response

zigbee2mqtt / hassio-zigbee2mqtt