oh my zsh for the root and for all user

I made symbolic links to my zsh files in my home dir, that seems to work fine:

ln -s $HOME/.oh-my-zsh           /root/.oh-my-zsh
ln -s $HOME/.zshrc               /root/.zshrc

Disclaimer (Updated 2020-3-9): Only do this on a single user machine as it will make a user able to run programs as root (see comment by Eliah Kagan).

Just run the install command as root user (after doing sudo su)

sh -c "$(wget https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh -O -)"

For anyone else with the same question, I would recommend a combination of Tummala Dhanvi's and Morton's approach. I installed oh-my-zsh both as root and as the user using the following commands:

User:

sh -c "$(curl -fsSL https://raw.github.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"

Root:

su
sh -c "$(curl -fsSL https://raw.github.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"

Then I created a symbolic link for the config file (run as user):

sudo ln -s /root/.zshrc $HOME/.zshrc

Make sure the user has permissions to read the file:

sudo chmod 744 /root/.zshrc

This approach allows for a shared config while keeping the system secure. You will, however, need root privileges to edit .zshrc