I've topped Zaino in the past and won't be doing it in the future. Initially the surface was slicker and the shine was a tad bit better, but I honestly think the downfalls are greater than the benefits. For instance, you can't add another coat of Zaino until the carnauba is gone. But the biggest factor is that carnauba contains a lot of solvents and oils. Over time these solvents can degrade the Zaino layers. I read somewhere that some carnauba formulations are roughly 75% naphtha (or mineral spirits). Such solvents will strip any sealant over time. So, I just don't think it's worth jeopardizing my Zaino protection for a carnauba look. The difference is too slight anyway....
Those that use Klasse with carnauba report better results with the combo, so my opinion strictly applies to Zaino...