Involved in lignin biosynthesis. Catalyzes the final step specific for the production of lignin monomers. Catalyzes the NADPH-dependent reduction of coniferaldehyde, 5-hydroxyconiferaldehyde, sinapaldehyde, 4-coumaraldehyde and caffeyl aldehyde to their respective alcohols. (E)-cinnamyl alcohol + NADP(+) = (E)-cinnamaldehyde + H(+) + NADPH Binds 2 Zn(2+) ions per subunit. Aromatic compound metabolism; phenylpropanoid biosynthesis. Homodimer. Expressed in the differentiation and elongation zones of primary and lateral roots. Expressed in the hypocotyl, cotyledon veins, vasculature of the first rosette leaves, hydathodes and trichomes. In stems, expressed in the vascular cambium and developing xylem tissues. Expressed in the style, anthers, stamen filaments, stigmatic regions in flowers, and abscission and style regions of siliques. Belongs to the zinc-containing alcohol dehydrogenase family.