Gah. I never used ZZ, despite using zz all the time, so I went to my editor and started hammering the Z key and ended up closing most of my files.
Well played. This is a nice way to check whether you read the article first or last.
What's up with thirty different ways to exit vim? ZZ, :q, :wq, :x, good lord! Vim must be the most effective editor as long as you want to not use it. :)
I think you'd enjoy this then: https://github.com/hakluke/how-to-exit-vim.