1/4 a^{a1,a2}_{c0,a0} b^{v0,v1}_{a3,a4} c^{}_{} eta1^{a4}_{a2} eta1^{a3}_{a1} a+(c0) a+(a0) a-(v1) a-(v0)
+1/8 a^{a1,a2}_{c0,a0} b^{v0,v1}_{a3,a4} c^{}_{} lambda2^{a3,a4}_{a1,a2} a+(c0) a+(a0) a-(v1) a-(v0)
-1/4 a^{a2,a3}_{c0,a1} b^{v0,v1}_{a0,a4} c^{}_{} lambda2^{a1,a4}_{a2,a3} a+(c0) a+(a0) a-(v1) a-(v0)