The Zoche engine has been in development for longer than I can remember - probably fifteen years or so. In all that time there has been little to demonstrate that the company has any intention of actually bringing anything to market. According to one of our German contacts, the operation is primarily funded by government grants and as such, seems to be set up only for the purpose of absorbing the money but little else.
Now, this is hearsay however, given the evidence to date, I'd say don't hold your breath.
If you're really interested in Diesel engines, look at organizations such as the one that is producing the Delta Hawk or several other developments spread across Europe - there are already several aircraft being developed or one or two which have already flown. One that comes to mind was being developed in Denmark in conjuction with an engine manufacturer, although at this point I don't remember the name.
I have a feeling Herr Zoche is on one of those people who have found a lucrative European Union developement grant and is milking until his retirement! Sorry Herr Zoch, I LOVE your egines, but please can we have some now?