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