As nouns the difference between zygodactyly and zygodactyl
is that
zygodactyly is (anatomy) the condition of having two toes facing forward and two backward, as in some birds and chameleons while
zygodactyl is (ornithology) any such bird (such as the parrot).
As an adjective zygodactyl is
having two toes pointing forward, and two pointing backward; zygodactylous.