How the menu is opened is mentioned quite prominently in the quick reference, which automatically pops up directly after the installation. :) In case you overlooked that so far, you should definitely read it. It has a few valuable hints.
Zooming the UI is not possible in Z-Buffer modes, you can however use the EdgePeek feature to access menus (press middle mouse button).
Adaptive Z-Buffer has an ‘autofocus’, otherwise both modes work similar.