Zbrush only uses hard edges, just subdivide that sucker, it won't matter once you're baking. When you are creating your lowpoly that is when you deal with edge hardness.
Using GoZ straight from Maya to ZBrush should also retain crease data.
If you have ZBrush 4r7, creasing has been substantially improved with the implementation of the new low poly modeling tools. It's much easier and faster to crease edges now.
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If you have ZBrush 4r7, creasing has been substantially improved with the implementation of the new low poly modeling tools. It's much easier and faster to crease edges now.