I can't find any reference to zincs in the 496 manual.
Isn't there any? Like somewhere in the raw water circuit/heat exchanger, for instance?

Besides, is it correct that there are the following 5 in Bravo I leg (new slanted style)?
And are all of them the same for standard and XR drive, or maybe the last one is different (just a thought, since the prop shaft is bigger)?
1) under the cavitation plate
2) ventilation plate on the front of the gearcase
3+4) on each of the trim cylinders
5) bearing carrier, between the prop and the gear housing

Thanks in advance!

nope!!!!

None in the engine water system.

The ones you listed on the drive are correct. Not sure if they are all the same for all models or not.