zsh has a comprehensive hook system available for these types of tasks¹(zshaddhistory in this case). It gives you more options to control how/when the history is preserved, and allows you to be more selective in when it should be written.

Possibly worth noting for others that you'd want to think this through if you're using any of the history eliding options(hist_ignore_space² for example), as one history file may contain secrets when you're really expecting that it wouldn't.

There is also a better interface to work with hook functions through the add-zsh-hook mechanism³, which allows stacking multiple hook functions together.

¹ https://zsh.sourceforge.io/Doc/Release/Functions.html#index-...

² https://zsh.sourceforge.io/Doc/Release/Options.html#History

³ https://zsh.sourceforge.io/Doc/Release/User-Contributions.ht...