1/2 a^{a1,a2}_{a0,v0} b^{c0,v1}_{a3,a4} c^{v2}_{c1} eta1^{a4}_{a2} eta1^{a3}_{a1} a+(c1) a+(a0) a+(v0) a-(v2) a-(v1) a-(c0)
+1/4 a^{a1,a2}_{a0,v0} b^{c0,v1}_{a3,a4} c^{v2}_{c1} lambda2^{a3,a4}_{a1,a2} a+(c1) a+(a0) a+(v0) a-(v2) a-(v1) a-(c0)
-1/2 a^{a2,a3}_{a1,v0} b^{c0,v1}_{a0,a4} c^{v2}_{c1} lambda2^{a1,a4}_{a2,a3} a+(c1) a+(a0) a+(v0) a-(v2) a-(v1) a-(c0)