Floyd but it would be interesting, Zivic is an underrated gem on film from that era but he’s too inconsistent to beat Floyd unless they had several encounters. His dirtiness and aggression would certainly put him off.
I think that this would be an interesting fight. If you read about Zivic, he won fights with his jab, body punches, counter right hands and left hooks. For all his reputation as a 'dirty' fighter, he was never disqualified. His greatest strength was his boxing IQ. Billy Conn, Ray Robinson, Henry Armstrong and Charly Burley all said that fighting him was like going to boxing university. When you look at Floyd, his greatest strength was his ring intelligence. At 147 he wasn't a puncher, bad hands took a lot of the pop out of his punches. He could still turn over a right hand though. He proved his ring IQ in fights with Andre Berto, Roberto Guerrero, and Victor Ortiz.
Floyd got his ass handed to him by Maidana. Zivic was on another level, he would literally make Floyd cry.