Hello @ayush.jha,
Apologize for how complex this process is complex as users must use a REST API resource and then manage the auth token with custom auth.
I was looking through the forum and found this post where one of our team members Ben walks a user through the process of setting up Zoho with Retool.
It looks to me much simpler than the Workflow work around that you linked which Darren was helping out on.
Going down that thread there are a could other users that have different issues related to this set up that are also addressed.
Victoria also provides a link to our docs on setting up custom auth to run the refresh flow when a new token is needed. Hopefully this helps! I am going to add a note for us to better support Zoho integrations as well.