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