If it’s a mission, there’s no chance Zabuza will show mercy. It’s his duty to kill, no amount of seduction is going to sway him. It’s that simple.
Kakuzu is the same. Seduction and anything bordering sexual just doesn’t appeal to him anyway, so it’s not really going to do much for him. It’ll annoy him at most, probably even hasten the process of killing them
Kisame is the only one who might take it into consideration, as long as it’s not a critical mission. He’d probably tease them and taunt them, still trying to intimidate them and make sure they know this is a dire situation, and he’s still on guard no matter what. That’s he’s in control. He still might kill them in the end though, but not immediately. He enjoys the taunting, and prolongs it as much as he can, kind of punishing them for pulling such a stunt in the first place. He probably wouldn’t take them up on the actual offer though, but he’d indulge their efforts anyway