Yes. ZBrush always creates its displacement maps with a mid point of 50% gray. Many image editing programs, however, have a setting that allows the program to manage colors for you when a file is opened. This means that the image editor is changing the the ZBrush map so that the mid point is no longer 50% gray. If you open a displacement map in another software and find that the mid point is not 50% gray, please check for such a setting and disable it.
Many renderers also require two separate maps; one for positive and one for negative displacement. ZBrush can easily convert the bi-directional displacement map that it generates into two separate maps for use with such an engine. There is a tutorial in the built-in help system called “Processing Displacement Maps” which explains how to accomplish this.
