Hi Orison,
I see your idea more clearly now and I have some ideas along. Again these are just conjecture as I have no real experience with what you're trying to do, just offering my thoughts.
In my head If you are trying to limit players ground based movement through thicker parts of the woods, you could just use zone borders creatively by having them outline your 'progression' through your zone. I wish I had a clear concise way to explain this, unfortunately I don't, so here's my best attempt.
Traditionally zones have a 'wall' or a portion of visually high altitude area that clearly blocks player movement and this is supported in OZ by the zone boundaries. If you are trying to direct players progression through your zone to given areas, or forcing them to traverse through certain challenges to get to other regions in the zone you could accomplish this by 'sculpting' your zone boundaries to match the 'map' of the areas and their flow. Rather than having a big clunky zone wall show the players where their limits are, it sounds like you want give them a more subtle environmental cue to them as to where they can't go.. If you outline via thicker tree covers / graphical contexts where 'areas' in the zone are and support
these visual cues with a zone wall you'll effectively have an 'open looking' zone while still directing player characters movements. This will prevent players from effectively 'levitating' to newer areas directly because the zone borders extend upwards farther than traditional EQ spells would allow them to traverse unless they blasted themselves up with lev on, even then they'd still have to follow the zone lines just they'd be able to avoid mobs assuming they could blast themselves high enough. To limit vertical movement (again I don't know for sure if this is possible, but from going through only the basic tutorial it might be..) try creating a horizontal plane that either has a clear texture or is not visible that doesn't permit actors to pass through it.
I have some other ideas as well how you could engineer this idea, however until I understand more your desired implementation it might be fruitless to post them
Kindest Regards~~