Zoho have just released 'Zoho CalSync', which is a free app for Android devices that synchs your Zoho Calendar events to your native Android phone calendar app.
This can be very useful if you prefer using the native Android app, with it's calendar like UI, but use Zoho Calendar for group calendaring and scheduling and still need to see what's going on for work, for multiple calendars.
If you have multiple calendars you can even select which ones to synch and show on your Android device.
Apple users can setup bi-directional synching between Zoho Calendar and the OS X calendar, and/or the iOS calendar for your iPhone/iPad, using CalDAV .