I would also imagine that allowing members to use Google login on Zoho would somewhat beat the competitive advantage that Google has in this regard- in allowing their members to share one login across all of their apps. Good move.
I wonder how Zoho is able to manage so many apps. Do you have many different development divisions? You mentioned that you have over 1,000 employees. How many does it take to maintain just one of the apps? I'm sure it will be dependent on that app itself, but if you would allow us an estimation merely for the insight.