Yes, it won't be easy to beat Real Madrid, but we have to remember how Manchester City gave an unexpected surprise last season and this could be Dortmund's motivation to be more enthusiastic about winning the Champions League title and most importantly, maintaining the quality of players is now much more important.
I agree with you that Terzic will definitely prioritize the UCL matches and will give the main players a little more rest even though the results are bad in the Bundesliga. The most important thing is that the UCL will be Dortmund's priority.
Manchester City is not the same as Dortmund, obviously, and you should know that. Manchester City were performing very well last season, while Dortmund are not, so you can’t compare what Manchester City did last season to what is about to happen between Real Madrid and Dortmund. However, even with the motivation, I don’t see any performance with Dortmund that will give them any hope of winning Real Madrid at the moment. Even Manchester City made it this way because they were in their best form that season.
So for me, I cannot guarantee Real Madrid winning this match, but honestly, Dortmund are not in a position to win them, and I believe they will not. Real Madrid have been consistently winning matches with even stronger Dortmund, so I doubt if they can concur.