I bought a Pi-zero 2 because I want to play with Unbound and want to keep my customized blocklists.
Can I just put in the SD card from my old Pi-zero w?
I would prefer to fresh install, because it would be on Bullseye, but I have failed at searching on how to how to migrate my blocklists and settings; much less will a simple save work after the upgrade.
I wouldn't recommend swapping SD cards.
Pi-hole's FTL binaries are target-built for specific CPU architectures, and there's quite a difference between the Zero's ARM11 (ARMv6) and the Zero-2-W's ARM Cortex A-53 (ARMv8) cores.
Just in case.
Sd swapping between those 2 devices will work. I did this swap from a pi zero to a pi zero 2 and it worked without any issues. Reinstall might be better but swapping works.