Not the 'quiet' way so much as the less cold-hearted way out. He disapproves Zero risking the Ikaruga to save Kallen (using the 'one person isn't as important as the group' argument that he argued *against* in S1 when it was Zero in trouble) and he disapproves of him not marrying Tianzi off to some Jap.
Diethard will inevitably commit some horrible atrocity because he thinks that's what the Zero he worships would do. And then when Zero gives him shit about it Diethard will spill the beans about his mind control hax, specifically how he used them on Euphie (since we know he figured that out in episode 24.)
Unless of course Lulu already sees this coming (not likely,) in which case Diethard will get KEIKAKU DOORI'd hardcore in the face by him.