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