a^{a1}_{a0} b^{a3}_{a2} eta1^{a2}_{a1} gamma1^{a0}_{a3}
+a^{a1}_{a0} b^{a3}_{a2} lambda2^{a0,a2}_{a1,a3}
+a^{a2}_{a0} b^{a1}_{a3} eta1^{a3}_{a2} a+(a0) a-(a1)
-a^{a0}_{a2} b^{a3}_{a1} gamma1^{a2}_{a3} a+(a1) a-(a0)