Lyon might be tough when playing other clubs but I don't think that their toughness is a problem to United. Manchester United is a team that when they are serious to win an important match, they do put in their best to make sure that they achieve victory. EPL matches might not be important to Amorim because he is using it as an experiment to know what strategy fits the players on ground. That's why you see him changing players to play in different wings and positions. However, this is an important match which Amorim knows he needs to win. He will definitely use his best winning strategy and players.
Amorim may be able to focus more on the Europa League, but every game will be important for him. That's because the poor performance in the Premier League is still his responsibility as a coach.
Facing Lyon, maybe everyone still thinks United is a strong team a few years ago. But I think, United also might not be easy to get a win.
Let's see how the quarter-finals will go. Facing Lyon, hopefully Amorim has the right strategy, as well as the players in their best condition.