Your next step is to rearrange so that you will get a pattern like this.

k(x[sup:1mps7c8w]2[/sup:1mps7c8w] - y[sup:1mps7c8w]2[/sup:1mps7c8w] + 4yz - 4z[sup:1mps7c8w]2[/sup:1mps7c8w])

Then work with it as the difference of two perfect squares, the first being a monomial and the second being a trinomial, a negative 1 being factored out of the trinomial.