The Raspberry Pi Zero’s USB port is an OTG port, meaning that hardware-wise programming it over USB should be possible. Well, some clever people over on the Raspberry Pi forums have worked out how to get the software working. Andrew Mulholland has now documented the process so that more people can do it. It’s still not for beginners, and you might want to wait for a more user-friendly solution, but if you have an application for programming over USB, give it a shot. You can read the instructions over on Andrew’s blog.