Complex sentence: In 1925, together with Moshe Beilinson, Katznelson established the Davar daily newspaper, and became its first editor, a position he held until his death, as well as the founder and first editor-in-chief of the Am Oved publishing house.
Split into simpler sentences: In 1925, together with Moshe Beilinson, Katznelson established the Davar daily newspaper, and became its first editor, a position he held until his death. He was the editor of the newspaper, "Davar", as well as the founder and first editor-in-chief of the Am Oved publishing house.