For a time from November 1941, Ziemer was a commentator on European affairs with radio station WLW out of Cincinnati. He later returned to Europe as a correspondent, embedded this time with General George Patton’s 3d Army.

At the Nuremberg Trials, an affidavit by Ziemer (an excerpt of one of his books), dealing with Nazi society in general and the education of youth in particular, was presented by the prosecutors. According to Reichsjugendführer Baldur von Schirach, this writing contained untruth and had “more importance as propaganda than it tends to be objective” and was “clearly inflammatory”.

Ziemer, who lived in California but summered in Lake City, kept busy as a writer of stories and articles and author of screenplays, contributing to the Saturday Evening Post and other popular magazines of the mid-20th century. He later served as a director of the American Foundation for the Blind as well as director of the Institute of Lifetime Learning. Among his key contacts in his charitable work was Hoagy Carmichael.