How do you sync customers between Zoho Books and Zoho Projects?

How do you sync customers between Zoho Books and Zoho Projects?

We have integrated Zoho Books and Zoho Projects using the ZSC keys etc. Now, how do you tackle the synchronization problems? The integration only synchronizes the invoices and the expenses!

Not just customers, how do you also ensure that the invoice numbering will be perfect? How do you ensure that your customer/client lists match all the time?