You can use Zaino in the sun. If anything, it helps with the drying time. I haven't had a problem with Zaino in the sun, as long as you apply a thin coat and wait for it to dry, you'll be fine. I still love the Zaino products (hence the reason I use it on my T4R), but I just had to try something new.
The Professional Polish is a very nice product. I used it to polish all the light housings, side mirrors (I have the black plastic kind), my exhaust tip and my black roof rack and it works very well. It's pretty much safe on anything. I haven't tried it on my paint though.
I barely used the EX and EX-P yesterday. So far, I'm impressed. I applied EX to half the trunk of our Corolla (silver) and EX-P to the other side and didn't notice too much difference in appearance, so I just used EX on the whole car. It went on easy and came off easy and looks pretty good. I hear that durability isn't as good as Zaino though and that EX-P is a better choice for durability.
Anyway, here's a picture of the Corolla.
I polished it with PB's SSR2.5 and finished up with EX.