Thanks for posting. The video the game linked really didn't provide much info on what routes actually are.
I just got Zygarde in step 3. No routes around so no idea how to progress further though
I tried to create a couple of routes in my area yesterday. They're currently marked as "under review." I'm hoping either those or some routes by other trainers (if any) will go live in the next week or so and I'll be able to use them for the Zygarde research.
It's a free special research. Niantic for whatever reason didn't do a great job of communicating this through their Infographic.