English Translation
Don’t be scared.
I can’t find this within the conjugation of zijn
Wikltionary lists it as an imperative form (see the inflection box):
zijn - Wiktionary, the free dictionary
It seems to be from wezen, an archaic form of zijn:
wezen - Wiktionary, the free dictionary
The direct article of wees also list it as the imperative of zijn:
wees - Wiktionary, the free dictionary