I've been thinking of knitting this myself. What you need to do is:
You cast on 75sts, right? Bind off the 9 central stitches. That is: work 33sts, bind off 9, work 33sts. Now you have to work the two parts separately. You bind off to create the armhole. On that side you will now decrease 2stitches (every 2 rows) 2 times, and 1 stitch (every two rows) 2 times: that's 6 stitches in all. Then work two rows and start increasing the same amount of stitches (6 stitches in all). Leave the stitches on the needle (you need an auxiliary needle to do this) and continue the other part of the armhole doing the same thing. Cast on the 9 stitches on the center and you'll have 75 sts again. Does this make sense?
Here is a graphic chart of the armhole (ignore that I wrote inc... it should've been decr=decrease...):
And here is how all the piece will look like: