While entirely in line with this topic, don‘t you fear some poor idiot is going to try just that? After all this is a respected tech and support forum.
To change default for you (not for root - which won’t have access to your .zsh anyway) , you do sudo chsh -s /bin/zsh ME
Beware of askubuntu. It’s a bit like signing up for a cookery course at a pig farm… and some solutions which suit Debian distributions are just waaaaay off track.
Anyway, after installing zsh, you should find a .zsh file in ~/home/ME - and when you do, it’s a good plan to make a new alias:
alias zshconfig='code ~/.zshrc &'
alias reload='source ~/.zshrc'
So it’s simpler to open and edit the config whilst using the terminal, and you can simply type ‘reload’ when you made an edit.
Next time our OP goes searching, hopefully a little more enlightened, search internet for ‘install zsh’ and ‘set zsh as default shell’ and ‘set zsh as default shell for me’.
As already said, to change the shell in KDE, you go into the terminal (Konsole) settings for the profile, and you change the shell command here.
Using chsh will not change the shell of KDE’s terminal. It will change the user shell only, which is not the setting used in Konsole, KDE’s terminal emulator.
I have to apologize @iiismaein , I replied exclusively to comment of somebody else, who made a joke that would have deleted the whole system if somebody would have followed it.
My response was not suited to help you with your problem.