Complex sentence: In 1925, when cartoonist Larry Whittington, creator of the comic strip "Fritzi Ritz", left to produce another strip, "Mazie the Model", Bushmiller took over to ghost it, before eventually taking over officially.
Split into simpler sentences: In 1925, cartoonist Larry Whittington, creator of the comic strip "Fritzi Ritz" left to produce another strip, "Mazie the Model". Bushmiller then took over "Fritzi Ritz", ghostwriting it, before eventually taking over officially.