HI Tom, there's a variety of different zoom methods currently:

Mouse wheel turning
Alt + Ctrl + Left drag up and down
Ctrl + Right drag up and down
Alt + Right drag up and down
Alt+Ctrl+Middle drag - if [View] AltCtrlMMBZoom=y is set in moi.ini
Shift+Middle drag - if [View] ShiftMMBZoom=y is set in moi.ini

There is not any built in way to change using the Ctrl modifier key with one of the F1-F12 "function" keys.

But you could probably get it to work by using an external key remapping utility program, like if you're on Windows look at AutoHotkey.

- Michael