That's odd - that's exactly what I did. I hold fn with one of the 4 arrow keys (down to the lower-right corner of the keyboard), and only fn-pgup/pgdn gave the effect of rotating the camera up/down - there's no zooming, let along rotating along z axis.
The only possibility of software interference I can think of is uControl 1.2 (for wheel scrolling emulation). I turned the wheel scrolling emulation off but the problem remained. Any more hint?
(it's really a pain not being able to zoom in/out)
Thanks.