4. In quadrilateral $A B C D$, points $X, Y, Z$ are the midpoints of segments $A B, A D, B C$ respectively. It is known that $X Y$ is perpendicular to $A B$, $Y Z$ is perpendicular to $B C$, and the measure of angle $A B C$ is $100^{\circ}$. Find the measure of angle $A C D$.

![](https://cdn.mathpix.com/cropped/2024_05_06_c43d6a72f2e2cc851afdg-2.jpg?height=426&width=623&top_left_y=1392&top_left_x=725)