You can import models sculpted using Pixologic™ ZBrush® into Mudbox. This approach requires that the ZBrush model have UV texture coordinates and that you export two .obj files from ZBrush: One from the base subdivision level, and the second from the highest subdivision level containing the high resolution sculpted detail. You import these two files into Mudbox after first recreating the same subdivision level structure as your ZBrush file.
Keep the highest subdivision level selected for the next step.
This imports the higher subdivision level model and recreates the highest subdivision level of the ZBrush model in Mudbox. When you step down using the Page Down key, you will have all of the sculpted information on the lower subdivision levels.