Dear Mr. Christian,
I came across a small trove of documents about the arrest of Ferdinand Zellner in St. Louis during the Civil War, and they seem to indicate fairly clearly that he did not serve in the Confederate Army. He was arrested at the same as several other people living in the same board house as he, and they were charged with being members of a secret society and plotting secession.
Zellner posted bond of $1,000 and was released after two days. Several friends — Judge Jonas Tebbetts who had known him in Fayetteville, Charles Balmer of the Balmer & Weber publishing house, and Judge Barton Bates of St. Louis — wrote to the provost marshall to say that Zellner had never supported the Confederate cause or served the Confederacy. Zellner in seeking to be released from his bond so that he could go to California stated the same thing: that he had never believed in the Southern Confederacy and had taken the Oath of Citizenship in 1862.
I'm still hoping to find a photo of Mr. Zellner, but so far no luck. According to one census record I've found, he had five children: Leslie, Chester, Sidney, Emily and Horace. But I haven't tracked down any grandchildren so far.
Hope you're well. Charlie Alison