They have two parts. Zinc fingers are man-made molecules made of a protein and zinc. Each binds to a specific DNA. Zinc-finger nucleases (ZFNs) are enzymes got by fusing a zinc finger to a DNA cleavage enzyme called a "Fokl". So the ZFN binds onto a specific DNA sequence, then snips it in two places. Regular cell enzymes stick the ends together, minus the bit snipped out (DNA repair).