This first time I used a mac where zsh was the default, I was confused for quite a bit of time when it would not run something I was used to doing. I kept looking up errors on the internet until I came across someone's post with a reply asking if they were using Terminal on a new OS X. Sure enough, this was a new mac as well. Now I know one of the first steps for me with a new Mac is change default shell. I'm way too old and set in my ways to care to learn a new shell. Choosing a shell, IDE, font, etc are games for youth.