Captain P. Usman completed the tally for Kerala, while Railways' Malayali player Rajesh netted both their goals.
It was Railways who drew first blood as Rajesh scored in the 17th minute making the most of a defensive lapse.
Joby completed his hat-trick in the second half, before Usman made it 4-1 with another header. Rajesh netted his and Railways' second goal but it was too little too late.
Playing their first game in the tournament, Mizoram would have been happy with a point in their first game while for Punjab, after a win in their opening game, a draw in this game consolidated second place in the group and they remain in contention for a semi-final berth.