Zaino is generally deemed better for lighter colored cars rather than dark cars. Zaino will make your car very shiny, which most people find more appealing on lighter color cars. On dark color cars, most people go for a deep look.
AFAIK, you can only get that with waxes. Zaino is not a wax, it's a polymer polish/sealant.
Having said that, I use Zaino on both of my cars. My Boxster is black, and my Firehawk is a medium, metallic orange (on the dark side of medium). I am very happy with the results. It gives the car a "candy coated" look. The main reason I use Zaino as opposed to wax on my cars is to save time. Zaino last around six months. Wax generally doesn't last that long. It takes me about 4 hours to do a "quick" wash on my Firehawk. A good wash with two coats of Zaino will take me all day. Therefore, I don't want to be doing that once a month.
Z-5 is usually what you use first. Z-5 helps hide minor scratches. Z-2 does less scratch hiding, so you use that when you get the car looking they way you want it with Z-5. Most people say that Zaino looks best with at least 5 coats of Z-5, then follow it up with Z-2. Of course, you want to use ZFX so you don't have to wait as long between coats. Z-6 is kind of a finishing/detailing spray. It is recommended to wipe the car down with Z-6 after every coat of Z-5 or Z-2.