How to make grounding in Khrushchev?

I want to change the wiring in Khrushchev (built in 1961). There is no earth wire. There are two entrances from two traffic jams.

Question: is it possible to attach the earth to zero in the shield? As I heard this can lead to the burning of zero in a bad situation. It seems that this was exactly what someone once had when the outlet had 420 V. However, the earth hanging in the air seems to me not beautiful either. What do you advise? Will an RCD at the entrance help in this situation?