So I was checking the data files ... and found something to fix that.
Instruction: Go to the 'Data' folder (in the game's main folder). Make a backup copy of MAPVIEW.TXT! After that, open this file.
You'll see the following lines:
Now you can make the following changes:PITCH 45
Save. Then start the game and load a scenario. Now you're able to zoom much further in and out.PITCH 45
(In case you cannot save the changes: This is because the .txt file is write-protected. Change this via "Properties".)
Of course you can experiment with other entries to find the right zoom adjustments for your needs. BTW: PITCH determines the camera angle. Change it's entry carefully, it can lead to ugly results.