`synchronizer` hasn't been ported to v3 yet. It's mentioned in the [Work in Progress section](https://zarr.readthedocs.io/en/stable/user-guide/v3_migration.html#work-in-progress) of the zarr v3 migration guide. _Originally posted by @dbashford-NOAA in https://github.com/OSOceanAcoustics/echopype/pull/1531#discussion_r2395629621_