Yup, it obviously makes difference but I was aware of that.I have the HTC Desire HD (ACE), not the Desire, if that makes any difference.
I couldn't find any difference on the file but I think I nailed the problem.
Apparently DHD uses a different code than other devices to mount system in recovery from a flashable ZIP. Can you please try to mount system manually in recovery before flashing the mod?
If it still doesn't work I could probably make a special build for DHD. Let me know.