Installing zsh and oh my zsh in termux on android – installing termux is easy, just goto the Google play store and install.
Once termux has been installed from the google play store, type the following to install zsh in termux
pkg install curl
pkg install zsh
pkg install git
Next, to install oh my zsh (from ohmyz.sh)
sh -c "$(curl -fsSL https://raw.github.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"
next, change your default shell to zsh