Yes, Terzic was a key member of Dortmund from 2018 to 2022, successfully leading them to the final, but they never won it. But well, at least he had some good experience in the Bundesliga. He's currently without a club. However, no decision has been made yet.
When we consider the progress made by Dortmund since Terzic arrived, we find that there has been actual improvement, although it has not yet paid off with major trophies. I believe the interesting part of the storey is how they were able to reach the stage of nearly being champions, so they have some impressive background in their game. According to reports, Leverkusen wants to hire a coach who uses a 3-4-2-1 formation, similar to the one Xabi used during the club's inauguration. Besides Terzic, several other names have been rumored, such as Raul, Claudio Giraldez, and Inigo Perez.
Source: Leverkusen want a head coach who will play 3-4-2-1.