Running iOS 7.0.4
Zimbra 8.0.5

I've tried looking on the internet but get varying solutions to fix this what seems to be should be a simple thing to do. What is the best method of allowing someone to view and edit a shared calendar on their iOS device?

I've created a shared account called ESEntertain on my account I then shared with them and allowed them to manage the calendar. As would be expected this works fine on the webmail client. On their iPhone or iPad however it doesn't show up. Now I know this is a bug because somewhere between here and there doesn't support shared calendars properly. I've tried a few things online, but what I'm asking is what have you verified to work in this scenario?