It def. isn't a wax or polish, you have to use both.
1. Wash
2. Polish
3. Wax
4. Clearcoat wax (optional)
Polish removes all the old wax and built-up dirt. If you just polish, it is like de-greasing a sword; if you leave it like that, damage will ensue. The wax is there to protect the paint.
I've been doing this process on my 540 for nearly 10 years, and the paint is still perfect. (aside from some road rash, but hey, it should have some with 150k on the clock) After I wax it, I can put the bottle of wax on the trunk and it will slide off, ditto for the roof. It takes a good 8 hours, even with buffers.
I have heard many good things about Zaino, but I have been using Meguiars for years with excellent results.