I think Z5 is more of a sunscreen and stronger protectant than Z2. I think Z2, that still has sunscreen, is always visually more appealing than Z5 so unless you need the longest protection you can find because your not going to detail your car again for a year or so, I'd stick with Z2. Z5 goe's on thicker and deeper and that's why people like it on dark colors, but it should be followed by Z2 for the shiniest Zaino trademark look. I like the combo of klasse AIO followed by klasse SG on dark colors too, especially if you have a couple of days to put extra coats of SG. Either of these combos are the best protection for dark colors but both can be topped with a good carnuba for the best look. If I could only put one product on a dark color I would put a carnuba, but I'd put it on every week. If you can't detail everyweek go with klasse/Zaino then wax when you can.