ITOT 41 Spring 2020 - THCS O - Additive practice Question 4

Let $n$ be an integer. If $x^2+y^2+z^2-xy-yz-zx=n$ has an integer solution, prove that $u^2+v^2-uv=n$ also has an integer solution. (The source reuses the letters $x,y$ for the second equation.)