ArmA 3 Forum, ArmA 3, ArmA 3 Config, ArmA 3 Missions, ArmA 3 3D Modeling, ArmA 3 Scripting, ArmA 3 Terrain, ArmA 3 Texturing, ArmA 3 Tools
Wilbur has particularly bad import options, there are tons of them, just none happen to be ASCII Grid (ASC) heightmap.
Terrain builder → Wilbur:
Wilbur → terrain builder:
Or the longer route without renaming, export HFZ, import to L3DT, L3DT export ASC, terrain builder import ASC.