For NAV there is an NDLM Authenticator which is only supported by Microsoft and not by anyone else. There is a 3 step authenticator to fetch data which requires very technical understanding of NAV to complete, which we have solved and done for this integration. Traditional API testing tools such as SOPUI do not work with the NDLM Authenticator which creates another significant layer of difficulty and expertise in this integration. Integrating NAV to Zoho came with some significant mapping issues, mapping the sales person and mapping pricing. Some fields exist in NAV that don’t exist in Zoho and vice versa. So we have fixed and remedied this issue as well.  – For example, there is no status module in the invoice module in NAV but there is in Zoho.