Hey Flashpan,
I struggled with this as well. It seems that when in Clickable cockpit mode, the mousewheel can only be used to rotate knobs in the cockpit and so on and not for zooming purposes.
After switching off clickable cockpit mode (LAlt - C), the zoom function can be used again. Unfortunately, you can no longer click stuff so it's not as useful as it could be.
Interestingly, after taking over control in a training mission, the mousewheel is mapped to the zoom function and you can still operate the cockpit with the mouse. Weird.
Jaxterass
