I am more interested in looks that durability since this is not a DD. It is on my dark metallic blue Mustang. If it's a waste of time I might as well skip one of the steps.
Putting wax on top of Zaino is not a problem; putting it underneath is. There will be no degradation of the Zaino finish. Looks are subjective and I haven't used that combo. Maybe some one that has will weigh-in.
I'm not a huge fan of topping sealants with carnaubas. I either go all sealant or all carnauba unless a customer makes a specific request. The simpler the process, the better.