More engine protection required when engine is clod and at starting time even in summer because 87°C is normal operating temperature of an engine.
therefor 0W gives more protection against 5W.
Yes 0W is thin, only at low temperature. at high temperature both are equal because both engine oil viscosity grade are 30.
ZIC OW is ILSAC GF-5 certified, GF means any type of gas fuel like CNG, LPG or Gasoline.