Just a heads up to you, though it will increase file size quite a bit, Poser accepts 16 bit TIF images as displacement maps. So save out to that if possible.

 

What I usually do for determining intensity level is I look at the Displacement Map menu in the ZBrush Tool menu for the intensity. In my case, it's usually 0.00x (where x is a serious of numbers). I jot down the numbers and then input those into Poser's displacement intensity. Sometimes I have to cut it by half or sometimes I just need to move the decimal point a bit but usually those numbers work or make for a good starting place (note that they change for each displacement map you make in ZB).  

 

At the moment Poser doesn't support vector displacement.