I could write a massive wall of text, but I'm about to go to bed so maybe tomorrow.
Short answer: if in doubt. Nose down.
For reference I use a minimum of 30-40% nose down in every corner at Phantom.
Zone pitching is corner/speed dependent. The Zone ship/mode is more eloquent in it's nature than normal racing,
so it's easier to see how the ship is reacting to the slope of the track at a given speed, making it easier to see when pitching
(down) is necessary. The only place I pitch up in Zone mode is Ubermall start/finish line after Zone 27 and on the hill after
the track splits to do the normal turbo shortcut after Zone...50?...60? I can't remember it's been a while.