The angled bar of the "Z" meets the horizontal bars at 30 degrees. So you can use an ordinary 30-60-90 degree triangle to place the horizontal bars properly.
To me the big difference is the slanted bar of the "Z" is completely contained within the width of the letter. When I trim the "Z" (as you can see in the photo above), I allow the extra 1/4" for the seam allowance. Those corners can't be cut off, or made narrower or I think the "Z" looks lame.
These are the first free-pieced letters I ever made. They're ok, but at that time, I didn't think I'd do too much with them. I disliked the Y's and thoroughly hated the Z's. I show them to you because it doesn't matter what your first letters look like. If you're willing to continue to experiment and learn, you can do some pretty cool stuff.