-a^{a0,a1}_{c0,c3} b^{}_{} c^{c2,c3}_{c1,a2} eta1^{a2}_{a1} a+(c0) a+(c1) a-(a0) a-(c2)
+1/4 a^{a0,a1}_{c1,c2} b^{}_{} c^{c1,c2}_{c0,a2} a+(c0) a+(a2) a-(a1) a-(a0)
-1/2 a^{a0,a1}_{c1,c2} b^{}_{} c^{c1,c2}_{c0,a2} eta1^{a2}_{a1} a+(c0) a-(a0)