Things I notice:
Zooming works well on hierarchical data structures, due to the following parallel properties between (perception) space and hierarchy:
and
Two disjoint parts of a hierarchy are independent.
ZUI implements a recursive partition of finite 2D space indexed by the conceptual hierarchy.
In my vocabulary, zooming is an example of non-discrete navigation. It can be made nonlinear/permissive by duplication. Permissive Navigation