Sal had said Dawn does not remove Zaino, and I've found it to be true, well at least it does not remove ALL the Zaino if you have significant number of coats on. I've used dawn to remove
Souveran topper and it still beads water.
If I want to strip Zaino, I would go the abrasive route. Although I've never done it before, I believe PPCL will do the trick.
By the way, I believe you like Z6 right? I think most people do. If you put carnauba topper over Z, you will not get the maximum result from Z6 anymore. That's another compromise for using carnauba topper.
If you really want to put on "something" over Z badly, why not try
Blackfire? I believe JPS said they seem to be compatible.