The most recent Märklin track plan book is the 0294 (paperback) or the identical 0296 (hardback). Although they appear to be currently out of print, copies turn up on eBay periodically and they are worth a modest bid.
The book details the Märklin mini-club track geometry and electrical technic. Starting in the middle of the book are three diorama layouts (a steam locomotive terminal, an electric locomotive terminal and a harbor scene). All three could serve as an entertaining Z-Scale model railroad in themselves, but there are provisions for connection to the outside world, too. Next are ten free standing Z-Scale model railroads that range in size from the very small to the very large. Following these layouts are six examples of Z-Scale modules that can help you get started with Z-Scale until there is time for a full layout. At that point, these modules can be incorporated into something bigger.
As mentioned on other pages, I’m a big fan of the 0290 layout book, which dates back to the 1970’s. There’s something about the stark geometry of the railroads which appear in this book: