For my first real Z-scale layout, I chose to base it on the design that John Armstrong wrote about in an article he did about what might be possible using Z-Scale modeling. I believe that this article was originally written prior to 1990, going back to when the Micro Trains product line was still sold under the Kadee brand. I found the article, Starting a second 50 years - with Z scale by John Armstrong, reprinted in 48 Top Notch Track Plans by Kalmbach Books (ISBN 0-89024-190-2).
The design is based on a fold-up concept whereby the majority of the layout is stored upright above a connecting shelf in order that its out of the way when not in use - a great space saving idea. In the drawing shown below, the shelf is to the right and the large blocks shown represent an elevated hinge system for allowing the layout to fold-up without concern for interference at the mating surfaces.
Areas where I significantly differed from John's published design include the approach to the yard section (shown on the shelf to the right) and the grading. I chose to reduce the number of tracks which would cross the hinge gap from 6 down to 4; with this change came a restructuring of the yard with the incorporation of additional switches at both ends of the shelf in order to get ready access to the third main line going through the yard.