@Rachio-newb - thanks for testing the prior install and making sure all the zones worked and the pictures.
I think the thicker green wire (black bundle) is the C(ommon) wire. I didn’t see the thicker black wire (black bundle) hooked up the the Rainbird controller in the before picture. So not sure why it is in the M(aster valve) terminal on the Rachio. Do you have a master valve in the system?
I do green to C, white to 2, blue to 3, yellow to 4 and orange to 5. I’m not sure what the Rainbird device is just below the controller (wireless rain sensor) and why it is connected to zone 1 (thin green wire) and the thin red wire is connected to the thicker red wire - maybe place the thicker red wire in 1.
Post what the Rainbird device is below the controller and I’ll look at that wiring scheme to nail it down (if an irrigation pro doesn’t beat me to the punch as they know what that device is and how it is wired).