There are several clear connections between the two scores, such as Clark's main theme (C-G, C-F, E) and the battle drums from the Black Zero Event, used during Bruce's scene in that same battle. But it's also been cool to uncover some of the more subtle links between the two scores. I wanted to share two of them here.
First, Man of Steel had the exhilarating piece "Flight" to encapsulate Superman learning to fly for the first time. The main themes from this piece showed up during the "Day of the Dead" sequence in Batman v Superman, but now it's tinged with sadness and melancholy as Superman is trying to deal with the sometimes troubling, sometimes deadly repercussions of his good intentions.
Second, Man of Steel had a great theme that was used for the final Superman/Zod battle, leading up to the ultimate decision of Superman killing Zod. If you follow the melody of this piece, it actually is used again in Batman v Superman. In BvS, it's also during the final battle scene, this time with Doomsday, and again it is Superman's ultimate decision that the entire movie has been leading up to, but this time the melody is set in a very dramatic, heart-wrenching style.
Amazing stuff, capturing the character development for Superman between the two movies.