It appears that DL's published fares require routing via the Atlantic, so you're not going to be doing a bunch of carrier mixing and matching. Thus, MU JFK-PVG-KMG-CCU is about your only option. JFK-DL-LAX-MU-PVG-MU-KMG-MU-CCU should also work, as would routing via YVR if you're booking after the date that DL's JFK-YVR service comes in. Prior to that, you're out of luck, as you'd exceed the four segment limit by taking a domestic connection.