At least one Zygon took the identity of Kate Stewart. Part of the group stuck on Earth after the ship landing in 1562, but the group retreated into a stasis cube and stayed there until the 21st century, where this Zygon took Kate Stewart's form.
In the Under-Gallery, the Zygon attacked Clara Oswald, but fell back when the latter got hold of a vortex manipulator. Later, three of the Doctors erased the memories of both the humans and their Zygon counterparts, and peace was restored. (TV: The Day of the Doctor)