The $ZSH folder already exists (/Users/rancohen/.oh-my-zsh). You'll need to remove it if you want to reinstall. code example
Example: oh my zsh git
sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"
sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"