Witch, princess, king, these characters were enough to make people come up with a western Fantasy story. Perhaps, anyone, who read a lot of western fantasy stories, would immediately decide to defeat the witch on the spot and then mount a white horse to ride a princess. Ah, no... it should be, mount a princess and ride a white horse, oh, god, that doesn't seem right either.
Unfortunately, Zhou Yu was a science student, who studied Liberal arts, so normally, his rationality was higher than emotion. So before there was actual evidence, even if there were Snow White and the little mermaid two princesses, he would not help them immediately.