This is my implementation of the Hurwitz Criterion in AEC. You can (hopefully) see it alive on my website.

Right now, it can solve the general case of the Hurwitz Criterion, and it can solve the first special case of the Hurwitz criterion, namely, when there is a zero in the first column of the matrix, but there is no row of zeros. It cannot yet solve the second special case of the Hurwitz criterion, when there is a row entirely of zeros (in which case, the system is either marginally stable or unstable, it cannot be stable).