I think I know the answer to this, but if I play the Russian card that says "DR turns into EX for the rest of the combat phase" and then later the German card is played that makes the result of a combat "DR", is the combat result "DR" or "EX"? I think it's a DR result, but it isn't logically clear since the cards don't actually contradict each other (one says B becomes A and the other says the result is B--somewhat different than if one says the result is A and the other says the result is B).
This is correct, the result is a "DR".
The Guderian card was played AFTER the Russian card, and Trumps it.
The revers is also true:
Ff the Guderian card is played First, then the Soviet players plays "Not a Step Back" right after, the Combat result will be an "EX".