I've always thought that ZUIs would be confusing for users. It's a completely modal interface. If you can zoom in infinitely or zoom out infinitely, it would probably be hard to determine where you are conceptually. Can anyone address this?
You can use space to have a visual organisation of things, but you don't have to navigate the space since it's virtual. You should be able to navigate suitable to your platform running the viewport.
Pinch-to-zoom, drag to move, two-finger tap to bring up list of applications to move to instantly on a tablet.
Keyboard based navigation and manipulation of the canvas if you prefer to not use a mouse on your workstation.
Click to drag and scroll-to-zoom to navigate with a mouse, when that is more appropriate, for example.
If an argument from authority means anything, Jef Raskin, one of the creators of the Archy system mentioned, is a large part of the reason modal UIs are Considered Harmful. If he thought ZUIs were an answer, well, you might have something mixed up.