Akm[k_,m_]:=Piecewise[{{(Ea + Ebxx2y2 + Ebyx2y2 + 2*Ee1 + 2*Ee2)/7, k == 0 && m == 0}, {0, (k != 6 && ((k != 2 && k != 4) || m != 0)) || (m != -6 && m != 0 && m != 6)}, {(5*(4*Ea - 5*Ebxx2y2 - 5*Ebyx2y2 + 6*Ee2))/28, k == 2 && m == 0}, {(3*(6*Ea + 3*Ebxx2y2 + 3*Ebyx2y2 - 14*Ee1 + 2*Ee2))/14, k == 4 && m == 0}, {(13*Sqrt[33/7]*(Ebxx2y2 - Ebyx2y2 + (2*I)*Mb))/20, k == 6 && m == -6}, {(13*(20*Ea - Ebxx2y2 - Ebyx2y2 + 12*Ee1 - 30*Ee2))/140, k == 6 && m == 0}}, (13*Sqrt[33/7]*(Ebxx2y2 - Ebyx2y2 - (2*I)*Mb))/20]