Corbier,
Test render out your displacements in Turtle for Maya.
The setup is faster an much simpler than in Maya/Mental Ray, there is further no need to convert the tif files from ZBrush in an external application before using them and it renders faster.
I posted a step by step for the ZSword some time ago at:
http://www.zbrushcentral.com/zbc/showthread.php?t=5660
For an evaluation license of Turtle, please visit:
http://www.illuminatelabs.com/eval.asp