I'm certain the methods being used here are just wrong. It looks like it's code generated by a symbolic algebra system. Chances are that using a more scalable methodology would eliminate the code size problem. For example, symbolic manipulations often have exponential space complexity in the depth of the expression tree, but automatic differentiation can do the required operation in polynomial time and space (often linear or log-linear).

Unfortunately, "no way to optimize" is basically a statement that the questioner is not interested in an algorithmic way to make the problem go away.