You can also have a zero downtime if during DNS Propagation if you know the tricks. Just don’t close your old host yet, make sure both old and new host has the same files and filepath (including database), and do your nameserver changes on your registrar to your new host without closing your old account first (which you can do it later when it has been fully propagated). The switch from old -> new host will be done seamlessly.

But make sure don’t post anything on your blog on the Propagation date to prevent losing your new posts.