If you've ever invested time in a level editor, there's a good chance you've started looking around your environment and considered how you might re-create it in a game. If you've ever invested time in a piece of zombie fiction, there's a good chance you've started looking around your environment and considered how you might survive an attack by the walking dead. The Project Zomboid Map Editor lets you explore both fascinations by enabling you to create your own home, office, or other environment, and port it into the alpha-developed isometric zombie survival RPG.
There's currently no official documentation for the tools, and very little in the way of community guides. The Zomboid development team have offered to answer people's questions as best they can in the forum post though, and they do link to this video of someone building Alcatraz in the kit.
Zomboid has been in alpha development for yonks, since long before Early Access, and from the beginning of the trend of early releases. In that time the game has grown from a few houses with a couple of guns, to a vast and complex RPG, with an open world containing multiple towns, a lot of fields, and even more brainless brain-hungry undead. It's an extremely unforgiving game, and in singleplayer, even more lonely and grim than DayZ. It's worth playing in its current state.
The team also deserve a lot of credit for their approach to selling their game. When Zomboid eventually came to Early Access, the developers took great pains to make sure the community were aware of the current state of the game, partnering with streamers to display as much of it as possible to anyone who was interested in buying. In the current climate, that's honourable.
On the official blog, the post announcing the map editor also talks about future update plans, including the continued shift to a 3D model system (which will enable better performance and lighting) and the wonderfully phrased "zombie migration systems", which controls the ways the undead spread themselves over Zomboids worlds. Important, if you want to practice surviving your escape from your home or place of work.
Living in Bath's Georgian basin, I'm probably fine in the event of a zombie apocolypse. The newly undead would all be retired second-hand bookshop owners still more interested in searching out expensive pots and pans than human brains. Perhaps I should build the town just to find out though.