Z would also be 63 degrees. Triangle WXZ is isosceles, as sides WX and WZ are marked as congruent. This means that the two base angles of the triangle (the bottom two) are congruent. You already know that one of the base angles, X (or WXY), is 63 degrees, so using this reasoning, the other base angle, YZW, is 63 degrees as well. I hope this helps!