a^{}_{} b^{c1,a0}_{c0,c4} c^{c3,c4}_{c2,a1} eta1^{a1}_{a0} a+(c0) a+(c2) a-(c3) a-(c1)
+1/2 a^{}_{} b^{c0,a0}_{c2,c3} c^{c2,c3}_{c1,a1} a+(c1) a+(a1) a-(a0) a-(c0)
-1/2 a^{}_{} b^{c0,a0}_{c2,c3} c^{c2,c3}_{c1,a1} eta1^{a1}_{a0} a+(c1) a-(c0)