I have been trying to follow the post mentioned in the title and I hit a problem. It was trying to switch from the normal zsh to the homebrew version. It would not work until I added the path to /etc/shells. I used the command below found from here (https://gist.github.com/derhuerst/12a1558a4b408b3b2b6e) and it then worked.
sudo sh -c "echo $(which zsh) >> /etc/shells" && chsh -s $(which zsh)