We have integrated Xero accounting software with Zoho Creator. This means Xero can be integrated with other Zoho services as well. We have a blog post explaining the details at http://www.aorborc.com/xero-zoho-integration-a-guide-for-developers-part1/
Xero Accounting Software
Xero.com allows you to automate your accounting process and minimize manual work.
Zoho Creator is a beautiful business application development tool. It helps you create software applications in minutes.
One of our clients wanted to integrate Xero accounting software with Zoho Creator. We have created/updated Contacts and Invoices modules in Xero.
We wrote a php wrapper to handle the authentication on Xero.
Technical Notes : (For developers)
We will be happy to share our sample code if you are looking to integrate these two services. Contact us for more help.