"... Her husband had preceeded her into eternity in the spring of 1878 ..."
Wm. Zimmermann's obit. was published in at least one of Milwaukee's German newspapers in 1878. It's indexed in "Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950).
Indexing of these papers started in 2007 and continues today.
Gary Rebholz, compiler/editor