you can probably dynamesh with high settings as is and get an ok result.
You might also try adding creases to the edges you want sharp - which look likes you want most of them sharp?
So goto window>relationship editors>crease sets then create a new crease set and add the edges you want to crease.
Here I've added half of this castle piece to the crease set.
You can import that creased maya file into zbrush or smooth it in maya by going to modify>convert>smooth mesh preview to polygons - then import that high res .obj into zbrush
That's what I would do with what you have anyway. PS - avoid going above 4-5 crease levels it can get very dense and cause slowdowns or crashes at higher levels.