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