The control bar is a dynamic interface. On this page, you can choose which Zoom Player functions appear on the control bar. Since each control bar button requires graphical elements created and since Zoom Player has several hundred functions, it is up to the Skin Designers to choose which functions are made available on the control bar.
One other issue of note is that Zoom Player stores different button sets for DVD and Media modes. To configure each mode, you must open the options dialog while Zoom Player is set to either Media or DVD mode.