http://zanshin.net/2013/09/03/how-to-use-homebrew-zsh-instead-of-max-os-x-default/
Out of the box Mac OS X version 10.8.x (Lion) comes with zsh version 4.3.11 (i386-apple-darwin12.0). However zsh is currently at version 5.0.2 (x86_64-apple-darwin12.2.1). Here's how to use the newer version.
Install zsh using Homebrew.
$ brew install zsh
/etc/shells
$ brew install zsh
$ sudo vim /etc/shells
/etc/shells
$ cat /etc/shells
/bin/bash
/bin/csh
/bin/sh
/bin/tcsh
/bin/zsh
/usr/local/bin/zsh
/usr/local/bin/zsh
To actually change the shell assigned to your user account run
$ chsh -s /usr/local/bin/zsh
Now you have the most recent zsh as your shell.
