Using Windows API, it is possible to attach a menu to the top of the GDK window and it is possible pop up message boxes and to display dialog boxes, both modal and modeless, which appear as separate windows and can contain any other standard controls. Mista has even wizarded a Dark GDK window into a child window of an MDI application which may be similar to what you want to do.
What is not possible is to put Windows GUI elements inside the DirectX surface which is controlled by Dark GDK since its drawing mechanism is different. Also, if you need to write a message loop which uses GetMessage (this is needed for tabbing in modeless dialogs and to use hot keys) then you will have a problem with the frame rate because GetMessage hangs the application update. So far the only workaround I know for this is to pump timer messages into the queue which helps somewhat. If you can do without hot keys and tabs then it's no problem.
From this thread you can download the Sephnroth's tutorial which shows you how to attach a menu:
http://forum.thegamecreators.com/?m=forum_view&t=137633&b=22
Mista's MDI application:
http://forum.thegamecreators.com/?m=forum_view&t=152825&b=22
The rest is standard Windows API usage, for which I studied the "Forger's" tutorial (
http://www.winprog.org/tutorial/), the MSDN site and several forums for code examples but I'm still far from being an expert - or even comfortable - with it.
Does that help? I didn't quite understand what you mean with zoom and mouse-click recognition.