Wich episode does zane threaten to tell the mermaids secret if rikki doesnt go out with him (OR WHATEVER HE SAID)

I don't think Zane ever threatens Rikki. I think آپ must be mixed up with something else.

Sorry!

In the Jewel thief season 3.He says that if they are not together anymore then he can not for sure keep her secret.In the end he says they can trust him.