It could have been very effective if the German Navy and German Air Force co-operated to some degree but they did not.
Also the aircraft started as an airliner and then converted to a bomber and was not stressed enough to carry the heaver loads and you can see many pictures of them with broken backs toward the rear of the aircraft.
For attacking shipping, it did very well and had decent range. I have not read much on how well it did on the eastern front.

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