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