I am following the steps mentioned in https://www.zoho.com/invoice/api/v3/oauth/#overview able to get access token and refresh token.
and not clear what to pass for invoice rest API for example How to get the list of invoices?
Zoho's documentation has an example call to list invoices : https://www.zoho.com/invoice/api/v3/invoices/#list-invoices
curl https://invoice.zoho.com/api/v3/invoices
-H "X-com-zoho-invoice-organizationid: 10234695"
-H "Authorization: Zoho-oauthtoken 1000.41d9f2cfbd1b7a8f9e314b7aff7bc2d1.8fcc9810810a216793f385b9dd6e125f"
So it looks like you will need to pass 2 items of information to get a list of invoices:
Here is a pseudo-code example with the 2 items in curly-brackets
curl https://invoice.zoho.com/api/v3/invoices
-H "X-com-zoho-invoice-organizationid: {my-zoho-invoice-organizationid}"
-H "Authorization: Zoho-oauthtoken {my-access-token}"