Barzakh is an impediment or obstacle between two objects so they cannot reach other. They might have knowledge of each other, but they cannot touch each other or arrive at each other due to this barrier or buffer called Barzakh.

Hijab is a membrane or screen or something alike that hides one object from another. There is a component of secrecy and hidden-ness in the word Hijab. Veil or membrane are good translations.

لسان العرب ابن منظور

برزخ

البَرْزَخُ: ما بين كل شيئين، وفي الصحاح: الحاجز بين الشيئين.

لسان العرب ابن منظور

حجب

الحِجابُ: السِّتْرُ.

حَجَبَ الشيءَ يَحْجُبُه حَجْباً وحِجاباً وحَجَّبَه: سَترَه.

وقد احْتَجَبَ وتحَجَّبَ إذا اكْتنَّ من وراءِ حِجابٍ.

وامرأَة مَحْجُوبةٌ: قد سُتِرَتْ بِسِترٍ.