You need to create an user with Access from the internet allowed in your FritzBox panel, after that:

• Download the script and add BoxUSER and BoxPW variables to your ~/.zprofile

  BoxUSER="your_user"
  export BoxUSER
  
  BoxPW="your_password"
  export BoxPW
  

• Make the script executable

  chmod +x /path/to/fritzBoxShell.sh
  

• Add this to your .zshrc

  alias fritzbox="/path/to/fritzBoxShell.sh"
  

• Restart your shell and then you can use FritzBoxShell

  fritzbox help