Since I just used
Blackfire yesterday, I can tell you that you are right about it being one of the better things to use. I haven't used any Z products yet but I have had a little experience with
Klasse. I had multiple coats of Klasse on a white car and topped it with multiple coats of carnuba wax. After one application of Blackfire my car looked better than it did with all those other coats of Klasse. Really depending on the color of your vehicle it will change which product will look better. On white I really like Blackfire. I've seen some darker cars look really good with Zaino. Klasse is a no fail type product. I think the jury will be out on this topic for a long time.
Welcome to the forum! What kind of vehicle and what color is it you are going to try this on?