The breakthrough is 2) eunuch b and eunuch d will not go at the same time. Here it can be clear that one of B and D is a thief and only one is a thief. Suppose B is a thief, then Ding is not a thief. According to the clue (1), A is not a thief, then C is another thief. But clue 3) shows that if C is a thief, then D is also a thief. It turns out that E, B and D are all thieves.

This assumption doesn't hold water because there are only two thieves.

So according to clue 2, Ping B was ruled out and Ding was determined to be a thief. According to the clue (1), one of Party A and Party B must be a thief, because Party B is excluded from being a thief, so Party A is a thief. To sum up, A and D are thieves.

If you don't understand anything, you can continue to ask, hoping to adopt it as the answer.