Aligning Equations

I've found a kludge to get me by, but still wonder what is the proper way to align a multi-line equation. Let's say I have this equation:

z = x+y = 4+6 = 10

I want this on 3 lines, with the '=' signs aligned. So I insert manual breaks and get this:

z = x+y

= 4+6

= 10

It seems logical to me that I should be able to go to Equation->Positioning, and select Alignment->'Left of ='. But this does not work. My kludge is to insert redundent z's, like this:

z = x+y

z = 4+6

z = 10

and for all but the first line, I set the font color for the z's to be white, so they are invisible:

z = x+y

z = 4+6

z = 10

What's the proper way to do this?