If you have Homebrew installed, you can do this.
# check the zsh info
brew info zsh
# install zsh
brew install --without-etcdir zsh
# add shell path
sudo vim /etc/shells
# add the following line into the very end of the file(/etc/shells)
/usr/local/bin/zsh
# change default shell
chsh -s /usr/local/bin/zsh
Hope it helps, thanks.
As far as I'm aware, you've got three options to install zsh on Mac OS X:
./configure, make, make install). I just switched the main shell to zsh. It suppresses the warnings and it isn't too complicated.
If you're not using Homebrew, this is what I just did on MAC OS X Lion (10.7.5):
Get the latest version of the ZSH sourcecode
Untar the download into its own directory then install: ./configure && make && make test && sudo make install
This installs the the zsh binary at /usr/local/bin/zsh.
You can now use the shell by loading up a new terminal and executing the binary directly, but you'll want to make it your default shell...
To make it your default shell you must first edit /etc/shells and add the new path. Then you can either run chsh -s /usr/local/bin/zsh or go to System Preferences > Users & Groups > right click your user > Advanced Options... > and then change "Login shell".
Load up a terminal and check you're now in the correct version with echo $ZSH_VERSION. (I wasn't at first, and it took me a while to figure out I'd configured iTerm to use a specific shell instead of the system default).
Source: Stackoverflow.com