The process for setting up a Z scan on DeltaVision is user friendly and integrated with the Resolve3D interface. The microscope is focused on the plane of interest. Then the distance above and below this Z level is provided to the experiment design program.
Sectioning (3D) experiments should be designed after you have manually acquired images of your specimen and adjusted exposure and other parameters until you are satisfied with the images.
For more about 3D experiments, see:
Sectioning Options (for specifying 3D experiment parameters such as spacing and thickness)
Stage Position Controls (for marking the top and bottom of the sample, visiting the middle of the defined region, etc.)
"Guidelines for Designing/Running a 3D Experiment" in the DeltaVision Imaging System User's Manual.