How to Migrate from ZHA to Z2M on the Same SLZB-06M Gateway (Without Re-Pairing Everything)

[Sarah_D]

Most guides on switching from ZHA to Zigbee2MQTT assume you're using a USB coordinator and tell you to re-pair every device from scratch. If you're running a SLZB-06M ethernet gateway, there's a lower-effort path that a few people in the Home Assistant community forum have pieced together, though it's still light on detail, so treat this as a starting point rather than a guaranteed walkthrough.
Why the naive approach fails
Just deleting the ZHA integration and spinning up Z2M on the same gateway doesn't work by default. Your Zigbee devices are bound to a specific PAN ID and extended PAN ID. If Z2M starts a fresh network with different IDs, your devices simply won't recognize the new controller and every one of them has to be factory reset and re-joined.
The workaround

Update your SLZB-06M firmware first. Firmware 2.7.1 and later added the ability for the gateway to associate with more than one client at once, which is what makes this approach possible at all.
Back up your ZHA coordinator configuration before touching anything. This is your safety net if the migration goes sideways.
Copy your ZHA network settings into Z2M. Instead of letting Z2M generate a new network, configure it with the same PAN ID, extended PAN ID, and network key that ZHA is already using. This is the step that avoids the re-pairing problem entirely.
Export your ZHA device list and use it to build your Z2M device configuration. This saves you from manually re-entering every device.
Run "interview" on each device from the Z2M UI. This is what lets Z2M actually recognize and populate details for devices it didn't originally pair.
Once you've confirmed everything shows up correctly in Z2M, disable the ZHA integration. Running both at once will give you duplicate entities for every device.

A safer alternative if you don't want to risk your live network
If you'd rather not experiment directly on your working setup, one option is to temporarily move ZHA onto a cheaper secondary coordinator, freeing up the SLZB-06M to become your fresh Z2M coordinator. You can then repurpose the original USB coordinator as a dedicated Zigbee router afterward instead of letting it go to waste.
A word of caution
This method hasn't been fully documented step by step by anyone who's actually done it end to end. The one person who described it didn't go into detail on how the "interview" step behaves in practice, so budget time for trial and error, and definitely don't skip the backup step.
Has anyone here actually completed this migration on a SLZB-06M? Curious what the interview step looked like in practice and whether all device types carried over cleanly.