There aren't a whole lot of diesel guys on here, unfortunately. Hooking a smoke machine to the intake (if you can make or borrow one) could help track down a boost leak, if that's what it is. From my limited knowledge of diesels, I'd also want to check the wastegate in case it's sticking open or something, and maybe check the fuel filter and any water trap the fuel system might have. I'm not familiar with how EGR works on a turbodiesel but I know it'll make gas engines run like crap when the valve (or the solenoid controlling vacuum to the valve) sticks open. I've temporarily blocked off EGR for testing purposes by just bolting a sheet of something between the EGR valve and the intake manifold where the gasket should be. Might be good to start there and see if it resolves the issue or just pisses off the computer (if it has one?) before committing to pulling the whole thing apart.
Your best bet, if you can get ahold of one, is the factory service manual. NicoClub is a great resource for manuals, but I think most if not all of what they've got are US-spec, so that's no help for your ZD. I've got a fragment of a service manual for some kind of van that covers the mechanical side of the ZD30DD, but it's non-turbo, doesn't include much troubleshooting (just "name that rattle"), and looks like it's for some kind of van. Hopefully you can find something better than that.
Good luck!