1/2 a^{}_{a0,a1} b^{a2,a3}_{} gamma1^{a1}_{a3} gamma1^{a0}_{a2}
+1/4 a^{}_{a0,a1} b^{a2,a3}_{} lambda2^{a0,a1}_{a2,a3}
+a^{}_{a0,a2} b^{a1,a3}_{} gamma1^{a2}_{a3} a+(a0) a-(a1)