[Laurent Rizzotti]

I can find two of your crew easily on the Volksbund database: Ofw Werner Walter Jauss and Uffz Hans Geib are both listed as being killed on 25 February 1945 at Zobten, Breslau area (apparently now Sobotka, Poland).

The two other men may be the two following cases I found on Volksbund:
1) Feldwebelleutnant Albrecht Voll killed on 25 February 1945 in Zobten. This rank is unknown to me, but it could your "Oblt Alfred Voll".
2) Fw Friedrich Franz Vogl killed on 25 February 1945 in Zobten. This could be your "Fw. Fritz Vogeln"

From a quick Google search, Zobten was on the frontline during the Breslau siege by Soviet forces, at least from 24 February to April if not May.

So the crash might have been on both Soviet and German held area. From the Volksbund entries, it seems that all four men above are listed as KIA rather than MIA, so were found and buried, even if their graves are now lost. This could indicate that the crash occured on German held ground.

PS: according to a map I found, on 6 May 1945, Zobten was on the frontline of the external ring of Soviet forces surrounding Breslau (ie not facing the city but the German front) and was in Soviet hands in the morning but was retaken by the Germans in one of the last big-scale (several divisions) German counter-attacks of the war.