Harzel
Adventurer
You vill tell me vere ze treasure is Dr Jones, you vill tell me NOW!
For as many times as I have heard people trying to do a German accent make "th" into "z", I don't think I have ever heard an actual German do it. Rather, what I have heard those with thicker accents do is make "th" into "d" or "t" or something a bit in between. Those with lighter accents often manage "th" just fine.
I think perhaps it is a confusion with French accents. Or I guess it could be a regional thing.
Or vehavehaf vays of persvading you... unfolds menacing coat hanger.