Even if it was better than GMail it would take at least a year or two to start replacing Gmail users, until there google will be workig harder adding new featur

Even if it was better than GMail it would take at least a year or two to start replacing Gmail users, until there google will be workig harder adding new features to Gmail what will make users don't switch to Zimbra. So Zimbra isn't Gmail's killer and won't be anytime soon.