Here is an infinite family of solutions resulting from setting $x=A z$ for integer $A$. For example set $x=2z$ and get $$g(y,z)=-(y^2 - 8*z^2 - z)*z$$ The quadratic factor is conic and [Wolfram Alpha gives](https://www.wolframalpha.com/input?i=solve+-y%5E2*z+%2B+8*z%5E3+%2B+z%5E2+++over+integers) infinitely many integer solutions in terms of powers of square root of two, e.g: $f(2*36,102,36)=0$ Potential attack might be to try rational $A$ and then find integral points on a conic with rational coefficients.