By October, Zemke was an ace and his "Wolfpack" squadron was developing new tactics of air combat that would shape how every other fighter unit in the world operated. One of the more innovative tactics was the "Zemke Fan". The Fan was an arrangement of 3 fighter squadrons. The lead squad flew low, with the next squad flying above, and the last squad flying high as a reserve for the other two.
The positioning and doctrine of this tactic meant the Zemke Fan could cut off interceptors from all manner of approaches without leaving escorted bombers vulnerable. The stacked squadrons could reinforce any squad below them if the need arose while the other regrouped.
Later, in August of '44, Zemke transferred to the 479th Fighter Group. The 479th was being issued the new P-51 Mustang to replace their P-38 Lightnings, and he wanted to get him some of that. Unfortunately, Zemke's plane was damaged on October 30th, and subsequently caught in a thunderstorm.
He had no choice but to ditch over enemy territory. Unable to evade capture, Zemke's role in Europe's air war was over with 17..75 victories credited and over 150 missions flown. His role of being impossibly useful, however, remained unchanged.
Just as an aside, Russian wasn't the only other language Zemke knew. His German parents meant he spoke the language of his captors. This was good for Zemke. Not only could he better communicate with the guards (and interrogators), he could also endear himself to them and start building up favors for himself and the other prisoners.
Though not as imperiled as, say, Polish Jews, captured airmen in Germany had two huge burdens to deal with.
First, there was a chance they'd be caught by the SS and not the Luftwaffe or Wehrmacht. The Luftwaffe and Wehrmacht drew from the greater population, and had people who appreciated the experiences of the soldiers and pilots they apprehended. The SS drew from dedicated members of the Nazi party, and encouraged a brand of hatred as of yet unmatched by any other organization.
The second is that the US and UK were bombing the ever-loving hell out of Germany's industrial infrastructure. The collateral damage was extensive. The Nazis used this fact as propaganda against the Allies, but it was also not an unreasonable thing to be upset about. More than one captured pilot and crew-member was subjected to torture (or a mob beating) by people wanting to get even for the bombing.