1.
$ vim .zshrc
plugins=(
...
docker,
docker-compose,
...
autoload -Uz compinit; compinit
2.
$ ln -s /Applications/Docker.app/Contents/Resources/etc/docker.zsh-completion /usr/local/share/zsh/site-functions/_docker
$ ln -s /Applications/Docker.app/Contents/Resources/etc/docker-machine.zsh-completion /usr/local/share/zsh/site-functions/_docker-machine
$ ln -s /Applications/Docker.app/Contents/Resources/etc/docker-compose.zsh-completion /usr/local/share/zsh/site-functions/_docker-compose
$ source .zshrc