What "resistance"? The Yugoslav Army didn't put up a fight and signed an armistice on the 17th of April. Are you referring to the German drive into the Balkans as delaying Barbarossa? A delay? Certainly...and a costly one. But this "resistance" that you speak of (if you're referring to the Chetniks and/or Partisans) had no effect on Barbarossa since all the important units were already driving into Russia and the Germans left only a skeletal force in the Balkans.
And the voice from the peanut gallery has been duly noted. Now go argue with them, not with me.