Consider following diophantine equation in $\mathbb Z[x,y,z]$ in three integer variables $x,y,z$
$$x^2+L(y,z)x+L_1(y)L_2(z)=0$$ where $L(y,z)$ is a non-homogeneous linear polynomial in $y,z$ and $L_1(y),L_2(z)$ are linear non-homogeneous in $y,z$ respectively.
In general such an equation is difficult to solve if $x,y,z$ are independent.
However suppose that there are univariate linear non-homogeneous polynomials $L'(y)$ and $L''(z)$ such that if $(x^*,y^*,z^*)$ is a solution to the three variable diophantine equation then
$GCD(L'(y^*),L''(z^*)=1$
There exists $a,b\in\mathbb Z_{>1}$ with $a|L'(y^*)$ and $b|L''(z^*)$ such that $ab=x^*$
With $\overline x^*=\frac{L'(y^*)}{a}\frac{L''(z^*)}{b}$ we have $(\overline x^*,y^*,z^*)$ also a solution
holds always. Then the unknown $x$ depends on $y,z$ and so in principle we should be able to eliminate $x$ and make this as a two variable quadratic diophantine equation.
One cannot say there is no small degree algebraic relation between $x$ and $y,z$ since we have already provided one by the quadratic equation. Unless we provide a different relation we cannot use elimination theory. However there is arithmetic relation. There is some hope. Is there a way to at least in principle reduce the problem to solving two unknowns through some functions coming from arithmetic?
What is the minimal degree of any other polynomial relation between $x,y,z$?
It is unclear if either of following two is possible at least when $L'(y)=L_1(y)$ and $L'(z)=L_2(z)$:
I. There is an explicit arithmetic function that relates $x$ and $y,z$.
II. There is any other low degree polynomial relation between $x$ and $y,z$. Note that by formulating the problem itself we have provided a quadratic relation between $x$ and $y,z$. So there is a polynomial relation. The problem is if there is another polynomial relation.
Is it possible to think in following way if solutions are considered in $\mathbb K$ where $\mathbb K$ is a ring? Over $\mathbb K=\mathbb Q$ or $\mathbb K=\mathbb C$ it seems the equation cuts a codimension $1$ object in $\mathbb P^3(\mathbb K)$. However if $\mathbb K=\mathbb Z$ then the equation somehow refers at most a codimension $2$ object with some symmetry in solutions? If so there should be a way to look at $2$ dimensional solutions over $\mathbb Z$ algebraically and if so any tools from arithmetic geometry applies here? Is there another way to think from algebraic or arithmetic geometry?