My Alterations!

Follow pattern with 6mm kneedles… until sleeves (in between marked stitches) are 54 st

Sleeve 54 st add 6 for ease underarm = 60 st
Knit round for R1
R2 Dec at beginning and end - k1, k2tog…. 3 from end ssk, k1
Dec every 6th row so R8, R14, R20 (12 times in all) until 36 st on kneedle.
Change to 5mm kneedles and k1p1 round for 27 rows then bind off using the no-flare stretchy bind linked below;

https://youtu.be/rWS77BKk5NQ for sleeve bind off

Had to improvise the zip as I didn’t want to machine or thread sew it on so I blanket stitched along both sides with same wool and then used the wool to sew the blanket stick to the vertical rib edging.