Use bus number 241 or 268 direction Glavni Kolodvor. Buy a ticket from the bus driver 15kn(2€). Validate the ticket by inserting it into the yellow ticket machine. Drive by bus to the last station to the King Tomislav Square
Now you need to take tram number 6 direction Črnomerac and you have two tram station to the Ban Jelačić Square
Your ticket is valid all the time in one direction!