Okay so I was rewatching The Falcon and the Winter Soldier, as one does. And I noticed this moment in episode 3. It was after Zemo killed Dr. Nagel and then came to their rescue.
Bucky looks at Zemo like he's trying to figure him out. Because, yes, he did break Zemo out of prison, because he thought Zemo could help against Hydra and the super soldier problem. But could he really trust the man not to take the opportunity to escape when it presented itself like this?
They had lost Zemo in the chaos of the garage fire, Zemo could have very well just slipped away. In Madripoor how easy it would be for him to disappear. He wouldn't need to go back to prison.
Instead of taking that opportunity Zemo helped them and then came to fetch them in a car. No wonder Bucky looks at him like he's seeing Zemo for the first time. He's getting to understand that Zemo is a man of his word. This is a man with steel determination and his own moral compass that might nor align with other people's, sure, but he still has a moral compass regardless. He might be many things, but when it comes to the super soldiers he doesn't play around. He will do anything he needs to do to finish the mission. I believe this is one of the reasons Bucky grows to respect him.