append your /root/.zshrc file with:
export EDITOR=whatever_the_prog_to_use
do the same for your at .zhrc of your regular user. For bash use the .bashrc file instead
Also, you can do
% sudo -E 66-env -t boot boot@ system
it that case 66-env you will use the EDITOR set at .zshrc (or whatever the shell used) of the regular user.
To test if the EDITOR variable is set, open a terminal and do
% printenv
it will display you all the variable set at your environment.