Griffiths Quantum Mechanics: Solving Angular Momentum with Commutators

[Bobbo Snap]

I'm having a lot of trouble following Griffith's quantum mechanics text. I'm in section 4.3 which discusses angular momentum using commutators. The text proceeds as follows:
[L_x, L_y] = [yp_z - zp_y, zp_x - xp_z]\\<br /> =[yp_z, zp_x] - [yp_z, xp_z] - [zp_y, zp_x] + [zp_y, xp_z]\\<br /> =[yp_z, zp_x] + [zp_y, xp_z] \qquad (1)
Ok, I follow the previous, the last step drops the two middle terms because they do commute. It's the next step I don't get:
[L_x, L_y] = yp_x[p_z, z] + xp_y[z, p_z]
How is Griffiths able to factor out the yp_x \text{ and } xp_y? When I expand eqn (1), I get:
[L_x, L_y] = yp_zzp_x-zp_xyp_z + zp_yxp_z - xp_zzp_y
I don't see how he can factor those out without commuting position operators with momentum operators which you can't do, right?

 

[Bobbo Snap]

Oh, never mind. I think I can commute momentum and position operators acting on different variables. So xp_z = p_zx.

 

[vela]

That's right.