I am not quite sure how a gun could have a French retailer name, a Francotte barrel (at least), Belgian and German proofs and a German name on it!

One possible path is :
Made in Belgium
retailed in Paris,
confiscated by the Germans,
reproved/remarked in Germany
confiscated by a US personnel and sent to the good US of A.

Also reading the history of Z-M, it seems that the area was under Russian authority in 1946. So the proofing with a German (formerly Nazi) stamp is kind of weird.

57973 is questionable as a Francotte number. Oh and the action looks vaguely teutonic to me.

Best regards,
WC-