Control Setup for 2x SBL2360 with 4x motors

Hi

My robot is a skid steer systems, with 4 motors setup. I have 2 SBL2360 motor controllers. I plan to have both front left motor and rear left motor to be controlled by 1 SBL2360 controller, while the front right motor and rear right motor is undercontrolled of another SBL2360 controller. As we know that Skid-steer controlling is similar to differential drive. I wish to have left SBL2360 to sync the speed control (RPM) of left motors, while the right SBL2360 control right motors to have same speed (RPM).

How shall i achieve this?

Best,
Samuel