After his service within German Luftwaffe and American prisoner of war, Zeitler studied physics in his hometown Würzburg.
The advisor of his dissertation "Investigation about the hard component of cosmic rays" was Helmuth Kulenkampff.
The quantitative electron microscopy remained the main topic of his research, which he continued at the Biophysical Department of the Walter Reed Army Medical Center in Washington, DC.
In 1977, he was appointed Scientific Member of the Max Planck Society and Director at Fritz Haber Institute in succession of Ernst Ruska.
In 1989, he received the honor of Distinguished Scientist from the Electron Microscopy Society of America (EMSA).