[AdieuToLogic]

> On par with the first time.

This was my experience as well. The --login flag was recommended in order to address concerns raised by @abathur.

> Whenever I've had noticeably slow zsh startup times in the past, it was almost always some plugin/extension doing something very dumb (e.g. stuff like full 'git status' in a large repo -- just takes time); not the history management.

Great point.

Unfortunately, my limited research suggests tracking down which plugin or extension is the root cause is a manual effort starting with the contents of the canonical zsh initialization files (often named .zlogin, .zprofile, .zshenv, and .zshrc).