Zimbra and OpenERP are very similar companies, very similar business models and have amazingly complimentary products.
I've searched around and can't find any reference to this which is surprising.
Has anyone ever successfully managed to integrate the two?
If not, where would you suggest a starting point would be?
Yes, we have done that. We're step by step integrating those two (also other applications) in our application service platform, so in the end it will feel like one big application.
But unfortunately I cannot tell you more for reasons of confidality.
You'll have to talk to my customer: Mr. Bernd Rodler, firstname.lastname@example.org