Please be aware that 3.4.11 has a quite unfortunate bug which causes
ZooKeeper to swap dataDir and dataLogDir parameters. If you configured ZK
to use separate txn and snapshot folders in these two options and plan to
upgrade, you'll experience that ZK is trying to load transaction logs from
snapshot folder and vica versa.
Fix is on the way, 3.4.12 will be released soon and it's recommended to
postpone upgrading ZooKeeper until that.
I think it'd be useful to add a similar warning message to the Releases