Proof of Median Properties

Triangle $ABC$ has sides $AB = 5$, $BC = 6$, $AC = 7$. Let $P$ be the midpoint of $AB$ and $N$ the midpoint of $AC$. Let $Z$ be the intersection of $BN$ and $CP$. If $AZ$ intersects line $BC$ at point $U$, find the ratio $BU/CU$.