You could also try using de Morgan's theorem and see if it simplifies anything.
Alternately, just implement a three input gate with two two input gates and invert the inputs as required.
Have you created a truth table for it?
My expression is simplified by Karnaugh map.
Aaah! I thought that was what you had modeled in the K-map.
Why not start with something like this:
x'y'z + x'yz' + xy'k' + xyk
x'(y'z + yz') + x(y'k' + yk)