These notes are for personal use, but feel free to use them if they are helpful to you.
This seems to be one of the easiest way to install flutter with .zshrc in terminal (Currently on macOS Monterey)
It also works if you received the following error:
zsh: command not found: flutter
So the correct way is to add to .zshrc by typing vim ~/.zshrc PATH="$PATH:$HOME/Flutter/flutter/bin" or export PATH="$PATH:/YOUR_FLUTTER_DIR/flutter/bin" then run source ~/.zshrc or just open a new terminal window