Elementwise multiplications with row sums appear to be slow

Modeling
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12

Sorry again, for brevity I ignored the initial conditions h as they wont affect the computation speed

    B[1:N,1] = rep_vector(1,N);
    B[1:N,2] = rep_vector(1,N)+(C[1:N,1].*A[1:N,1].*B[1:N,1]);

Without this initial condition yes there is only one solution, the trivial one of zero