Zimmer's path to work on the Soviet atomic bomb project was through a prisoner of war camp in Krasnogorsk, as was that of his colleagues Hans-Joachim Born and Alexander Catsch from the "Kaiser-Wilhelm Institut für Hirnforschung" (KWIH, Kaiser Wilhelm Institute for Brain Research, today the "Max-Planck-Institut für Hirnforschung"), who worked there for N. V. Timofeev-Resovskij, director of the "Abteilung für Experimentelle Genetik" (Department of Experimental Genetics). All four eventually worked for Riehl in the Soviet Union at Laboratory B in Sungul'.