They're really not that hard. I bought some great yarn, this magical algorithmic sock yarn from Germany that automagically makes stripes in what you're knitting -- no changing yarn. I'm using this pattern, except that I skipped the extra long cuff & just started with the short cuff. It's great to be able to make custom-fit fingers.
I was warned by the daughter of a very seasoned German knitter that zippers were hell. She'd done one once -- 20 years ago -- and swore them off forever. Hmmmph.
With lots of perturbation, I pored over online tutorials here, here, here and here. I ended up with a hybrid of links 2 & 4, mostly, and remembered many things from my sewing days. First, I tacked the stripes together with small pieces of red yarn. I then whipstitch-basted the fronts together with the silver yarn, being careful to stay in the same row for an even edge.
Turned the sweater inside out, then pinned the zipper -- face down -- onto the flaps from the front pieces. I then whipstitched the edge of the zipper to the edge of the front flaps & then basted down the centers of the zipper on each side. The pins came out, I turned the sweater rightside-out again, and then came the moment of truth of removing the yarn basting.
Beautiful! The stripes matched! I spent several hours yesterday then going over the basting and backstitching the zipper in place by hand. Not going to take it near a sewing machine after all that work...
The sweater is warm and cozy, and the lengthening adjustments I made seem to have worked perfectly, albeit a little bunchy in the sleeves. It's not been blocked yet, though, so that can probably be remedied. The body, however, is bespoke!