ɪn ðɪs kˈeɪs, ðɛɹ ɪz nˈoʊ juːnˈiːk tʃˈɔɪs ʌv kwˈɔːɹɾɪk ɪnvˈɛɹiənt æz ˌɛni pˌɑːlɪnˈoʊmɪəl wɪð ænd nˌɑːt bˈoʊθ zˈiəɹoʊ səfˈaɪsᵻz.
In this case, there is no unique choice of quartic invariant as any polynomial with  (and  not both zero) suffices.