public void setZoomInTrigger(Trigger... triggers) {
        inputManager.deleteMapping(CameraInput.CHASECAM_ZOOMIN);
        inputManager.addMapping(CameraInput.CHASECAM_ZOOMIN, triggers);
        inputManager.addListener(this, CameraInput.CHASECAM_ZOOMIN);
    }
Sets custom triggers for zooming in the cam
default is
new MouseAxisTrigger(MouseInput.AXIS_WHEEL, true)  mouse wheel up

@param triggers the triggers to assign
jme3-core/src/main/java/com/jme3/input/ChaseCamera.java