Before joining the US Army, Zeck—a lawyer—worked for the Board of Economic Warfare. In 1946, he was hired to work on preparations for the Nuremberg trials. In his search for documents pertaining to the I. G. Farben company's involvement in the war, Zeck also met attorney Belle Mayer, his future wife. Both Zeck and Mayer were involved in preparing the indictment in the I. G. Farben trial held at Nuremberg.
There were two ways in which we acquired evidence. One was through paper, documentation, which was really the bulk of what we did in all of the trials and the other was through interrogation. And the interrogation process proceeded exceedingly well, unlike trying to prosecute war criminals in Bosnia, because these people were our prisoners. We had won a war and they really didn't have any alternative, so that when you interrogated them and you had some documentation when you did interrogate, I think you could expect for them to tell you the truth, particularly since they all had one defense: superior orders, "We had to do it because Hitler ordered it" or "We had to do it because the head of the company ordered it," you see. But you still didn't make a case that requires individual knowledge and individual acquiescence and responsibility, without proving that the individual defendant did know what he was doing and did willingly collaborate with the Hitler government.