I used your guide to link my zoho and gmail accounts. Your guide is great, but I did have a fairly substantial hiccup that drove me nuts for about an hour.
I was getting alternating authentication error and timeout errors. The issue was the Zoho security settings.
I had to take the Zoho disable the Zoho Two Factor Authentication, and as soon as I did that everything worked perfectly.
I did not see any mention of this in your instruction so I wanted to put that out there in case others had the same issue. Thank you again for putting this guide together.