something else to consider is Zbrush by default will flip your UV's verticaly,so you'll need to flip them back before exporting(you can do this in the ZB alpha pallete with the 'Flip V' button)

here's an example of the node setup for zbrush generated maps..as Baggins mentioned you'll need to tell Poser to use 'outward' & 'inward' displacement via the subtract node

Cheers
Stefan

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