Yes, it can be done quite easily, but if you plan to run them simultaneously keep in mind that battery drain will be raised exponentially! First thing to do would be to increase the size of the jumper connecting the positive post of battery #1 to the negative post of battery #2 to a minimum of #4 copper. Personally, I'd run #2 or even 1/0. The negative leads of both motors will connect to the negative post of battery #1, the positive lead from the 24 volt motor will connect to the positive post of battery #2, and the positive lead of the 36 volt motor will connect to the positive post of battery #3. You should be able to use the existing jumper from positive post of battery #2 going to the negative post of battery #3 without an issue as long as it it at least #6 copper, but would recommend #4 copper. Also recommend utilizing a breaker of recommended size for each motor.
Steve "Hawker" King
In remembrance of those that gave the "Ultimate" Sacrifice!