Maybe they won't,but I'm not concerned if they do,as both can be class for 90 mins or 70 or whatever it takes to progress.
However play Zinchenko or Gundogan or whoever it takes to keep them "happy" and we are asking for trouble.
Had Pep played our most in-form players today, he should have rested them against Arsenal and play them just 3 days before Madrid against Burnley since not playing 10 days would be too much and some might lose rhythm. That's the simple logic behind the selection apart from keeping as many players happy as possible. As regards Gundy, he was one of our better players at Bernabeu, see the MotM thread.