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 after capturing the real Kate.
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)