David Maitland has worked out the series of commands and edits that you need to carry out in order to automatically make your Raspberry Pi headless and available on your network from first boot-up. It involves using a Linux computer to edit files on the SD card before you put it in your Zero. There is still no way of doing this from Windows, however, so your actual ability to use this still relies on having a Linux computer at your disposal. Read more here.