I think many people face the problem that to level the terrain, you have to overlap zones to maintain a consistent height level. Maybe it would be worth adding the ability to see the selected global ground height level? I think that would make things a lot easier for many players.
(The height level would match anywhere, no matter where you started leveling)
Also, it would be super cool to bring back the height level slider — trying to aim at points on a 4K monitor is an absolute pain.