which are worked separately and then joined to form the front yoke

The button holes are constructed at the end by widening up a hole in the knit fabric (and are thus not worked as you knit the button band)

6 mm zipper

which in the given example would give you 30 cm [11¾ inches] of positive ease

As an extra detail

Everyday Socks LANGUAGE:Norsk which are worked separately andThe Everyday Socks are worked from the cuff to the toe. The socks are worked in stockinette stitch either in stripes or in one solid color. The heel is shaped with short rows. Sizes: EU shoe sizes: 35 36 (37 38) 39 40 (41 42) 43 44 US womens shoe sizes: 5 6 (6 7) 8 9 (9 10) 11 12 Gauge: 30 sts x 40 rows = 10 x 10 cm [4 x 4 inches] in stockinette stitch on 2. 5 mm [US1] needles Needles: Double pointed needles: 2. 5 mm [US1] (or a 2. 5 mm [US1] 60 or 80