Involved in lignin biosynthesis. May catalyze the final step specific for the production of lignin monomers, like coniferyl alcohol, sinapyl alcohol and 4-coumaryl alcohol. (E)-cinnamyl alcohol + NADP(+) = (E)-cinnamaldehyde + H(+) + NADPH Binds 2 Zn(2+) ions per subunit. Aromatic compound metabolism; phenylpropanoid biosynthesis. Homodimer. Reduced lignin content, and modified lignin of reddish-brown color. Belongs to the zinc-containing alcohol dehydrogenase family.