Attach to any old TMUX on exit if its not a tty (only in pty and anything else)

.zshrc

# TMUX
if [ -z `tty | grep tty` ] ; then
    if which tmux 2>&1 >/dev/null; then
        # if no session is started, start a new session
        test -z ${TMUX} && tmux

        # when quitting tmux, try to attach
        while test -z ${TMUX}; do
            tmux attach || break
        done
    fi;
fi;