Zoho Invoice is an online accounting software which helps you to get your invoicing done. Zoho Invoice has all the essential functionalities related to invoicing like quotes, estimates, multi-currency support, online payments, credit notes, invoice templates, an iPhone app for invoicing and an android app for invoicing from android & other mobile devices and multi-lingual support.
On the other hand, Zoho books are complete online accounting software that lets you get your accounting done online. You can keep up your income and expenses, manage your banking and credit card transactions and work with your accountant online with Zoho Books. In Zoho books, you will see a complete invoicing module which includes all the features of Zoho Invoice.