German to English Bus/Financial Finance (general) Power of attorney

All,
I am translating a Bankvollmacht from Germany. Target audience is Australia.

The passage in question reads:
Diese Vollmacht erlischt nicht mit unserem Tode, bleibt vielmehr für unsere Erben in Kraft. Der Widerruf eines von mehreren Erben bringt die Vollmacht nur für den/die Widerrufende(n) zum Erlöschen; die Bank kann verlangen, dass der/die Widerrufende sich als Erbe ausweist.

The first half of the second sentence in the passage appears to describe the situation where one of several heirs revokes the power of attorney. But if this is the case, why does the sentence not read “Der Widerruf ***der Vollmacht*** eines von mehreren Erben…”? or “Der Widerruf ***durch*** einen von mehreren Erben…”?
In the second half of the second sentence in the passage, I cannot make sense of the expression “bringt die Vollmacht nur für den/die Widerrufende(n) zum Erlöschen.” I could understand it if it read “bringt nur die Vollmacht des/der Widerrufende(n) zum Erlöschen.”

My translation so far reads:
This power of attorney does not lapse with our death, but remains in force for our heirs. The revocation by one of several heirs causes the power of attorney to lapse only from the person or persons who revoked it; the bank may require the person who revokes it to prove that he/she is an heir.
However, my described difficulty in understanding the source text has me in great doubt of the correctness of my translation.

The wording appears to be commonly used as I have found it identical or very similar in the fine print of contract conditions from several banks or credit card providers.
https://www.die-erbrechtskanzlei.com/widerruf-einer-vollmach... discusses the situation of an inherited power of attorney and its revocation.

I will be very grateful for any comments.

Peter