Sir, he is actually referring to Ernakulam(people in Kerala usually refer to Ernakulam as EKM and Trivandrum as TVM).
His doubt is whether he can change the boarding point to CAN for his confirmed ticket from ERS/ERN to NZM and travel till CAN in other train without buying a ticket between ERS & CAN.
Answer- You can't travel with the same ticket in another train if the boarding point has been changed. You gotta buy a ticket for traveling between ERS & CAN..