Oh, to be able to be a fly on the wall. Zemo had already made up his mind about Bucky. He had already decided that he liked him as a person and no longer held animosity towards him. However, Zemo was still interested in watching his interactions with others. The baron liked knowing that he was right about the Winter Soldier; that Bucky was more than HYDRA had made him. And interactions like this just reaffirmed what he already knew.
But Will's words made Zemo curious. Will still had not elaborated on what he meant by 'handling the issue'. They could have run away from Abigail's father. Could have simply maimed him, could have killed him. Judging purely off the context clues he'd been given, Zemo was starting to feel like it was the latter of those options. And Will appeared to be comfortable discussing the matter, so maybe he wouldn't mind sparing a few more details..
"Tell me more. Did James.. help you handle Abigail's father?"