Hm. Some interesting thoughts in this thread. Here's how I'd generally address some of these:
There is no "roll" in moving between zones that lack terrain features between them that your character sheet can't automatically overcome (things with legs can walk across a parking lot, things with wings can fly over fences, aquatic creatures can cross a river).
This one's false. You get one free shift of movement as a supplemental action; if that's not enough to change zones, then you need to make an athletics action to move.* And for this, it doesn't matter if the zone border is a 'natural' one (say, from an inconveniently placed shrubbery) or resulting from a block (say, from an earth wizard raising up a wall in the middle of the parking lot) - either of these will prevent movement.
* Footnote: some exception may be made for creatures with extremely high strengths; there are rules for what you can break (I think it's something like might -8 or somesuch?) without requiring an action. Of course, this requires the block be one that can be just punched through with raw strength; a black court vampire might not slow down for a locked interior door (just breaking through it), but a threshold or act of Faith would not be so vulnerable.
Now, say that wizard brought up a wall - and it's a +6 block, versus your athletics skill of one. You can't directly overcome the block; even with a +4 on the dice, you're out of luck. What you *can* do here is spend an action to try to remove the block, breaking it down with might or magic or maybe just scrounging up a fire hose to short out the wizard's abilities. That's a basic opposed roll - and if you take the -1 penalty for a supplemental action, then (assuming your roll succeeds), you'd be able to break the block and move one zone after.
For blocking things that aren't measured in shifts - such as most shapeshifting - you'll want a compel. Succeed at a maneuver, use your free tag for effect to trigger a compel. In some cases, this'll be a freebie; put up a circle around a wizard who casts shapeshifting spells, and (unless he saw what you were doing and prepared a counter-maneuver to draw in power or something), that's that. In other cases, it'll just fail - put up a regular circle to try and lock down a loup-garou, and you're just out of luck. But hey, that's compels for you.
Now, there are some cases where you can clearly block shapeshifting with an actual block action. For example, the Human Guise power mentions discipline checks to maintain a human appearance; you could use intimidate skill to incite such anger that your opponent can't shift back, for just one example.