I have seen that many times, a German word is spelled with an "s", but it is read like an English "z".
Moreover, every time this happens, the Dutch cognate word is spelled with a "z". (But not the English and Scandinavian cognate words).
SÜD (Dutch: zuid, English: south, Swedish: syd)
SÜSS (Dutch: zoet, English: sweet, Swedish: söt)
SEIN (Dutch: zijn)
SIE (Dutch: zij)
SO (Dutch: zo, English: so, Swedish: så)
SIEBEN (Dutch: zeven, English: seven, Swedish: sju)
What happened, linguistically speaking? Why, and when?