Currently Ctrl-Shift Mousewheel does a general zoom: as well as zooming text it also zooms thumbs, preview pane width and folder bar width.
I can see the logic to changing the folder pane width since the contents are mostly text, but changing the preview pane and thumb size are both in my experience undesirable, the thumbnail size in particular is already sized to what one wants by ctrl-wheel and so you really just want Ctrl-Shift Mousewheel to be a text zoom (possibly rewidthing the folder bar). Usually it's being used just for seeing more text.
If the existing method has some following, maybe it can be resolved by some extra zoom action values -
* Zoom Text
* Zoom Text and Folder Bar
I think "Zoom Text and Folder Bar" might be best as default.
I would say that most of my own zooming is in practice just for the purposes of a particular element - just the results list, or just the folder bar, or just the status bar. This can be for various reasons; we probably all have a comfort size for font size, which can vary with time of day and light levels, but then sometimes you want to sacrifice some of that comfort to see more lines or width on one of the components by text-shrinking, however you don't want to sacrifice that comfort on all the panes and bars, just one particular component. So for example, you shrink the Folder Bar font if you particulary want to see a lot of folders for some purpose such as dragging and dropping, but you don't want the results list to shrink with it. If your eyes are tired you maybe want to size the results list up for comfort but you don't want everything else sizing up too - the menu for example has fixed items which you know whatever their size, the folders in the folder bar you probably know, so they can happily just stay the same size. In this respect I'd always be keen on an assignable "Zoom Component Text" which just zooms the text of the component under the cursor (which might even be the status bar).
Hopefully some of this thinking will be useful
David