ϕ12(a,bc;q,z)=(b,c/a,az,q/(az);q)(c,b/a,z,q/z;q)ϕ12(a,aq/caq/b;q,cq/(abz))+(a,c/b,bz,q/(bz);q)(c,a/b,z,q/z;q)ϕ12(b,bq/cbq/a;q,cq/(abz)),