The older Raspberry Pi's (Pi 1, Pi 2 and Pi Zero) couldn't boot from a USB-device, but the [Raspberry Pi 3 has support for it][1]. The Raspberry Pi Zero W is a remake of their older board but it's newer than the Raspberry Pi 3.

Is the Raspberry Pi Zero W compatible with the new bootcode? Can the Raspberry Pi Zero W boot from USB?

[1]: https://www.raspberrypi.org/blog/pi-3-booting-part-i-usb-mass-storage-boot/