How can I find the solution to a multi dimensional struct function in Matlab?

Hello,

I have a multi-dimentional trained machine learning regression model (trained by the Matlab regression learner). It uses 6 variables in total.

Say this function is f(x), where x is a vector containing all 6 variables.

I want to solve this function at f(x) = Y, in other words, solve function f(x) for all values on the intersecting hyperplane Y, the red boundary in the attached figure.

Any ideas how I can solve for all variable values of x along this intersecting boundary?

Thanks!