From ZBrush Info

Download

 Download Displacement Exporter, Multi Displacement 2 & Documentation Here (MAC)    

 PC Version is installed in the ZBrush 3.1 Update

Installing the Displacement Exporter

1. Extract the zip file to anywhere on your computer.
2. Move the contents to the ZStartup/ ZPlugs directory. If your ZStartup directory does not have a ZPlugs folder, create it.
3. Launch ZBrush
4. The plugin will place two buttons in your Alpha palette and a new sub menu, Multi Displacement 3, in your ZPlugins palette.
5. You can move the documentation, ADE4.PDF, anywhere you want.