Open the project "C:\Delphi\Zip\Demo1\ZipDemo1.dpr" and try to compile
it. When I did it, I got the following error:
 
       [Fatal Error] mainunit.pas(632): Internal error: C3517
 
This is a compiler error and I'm reporting it to Borland. I isolated the
problem and it apparently occurs when optimizations are on (the default)
and you explicitly cast an Int64 object property (not a constant or
variable) to Int64. It might not occur in your version/build of Delphi,
but if it does, there would be two solutions.
 
  1) Turn off optimizations around the ZipMaster1Progress procedure:
 
  {$OPTIMIZATION OFF}
  procedure TMainform.ZipMaster1Progress(Sender: TObject...
    ...
  end;
  {$OPTIMIZATION ON}
 
 
  2) Or (better) remove the unnecessary Int64 castings:
 
  // Step := Integer(Int64(TotalProgress1) * Int64(10000)
  //         div Int64(TotalSize1));
  Step := Integer(TotalProgress1 * 10000 div TotalSize1);
 
  // Step := Integer(Int64(TotalProgress2) * Int64(10000)
  //         div Int64(TotalSize2));
  Step := Integer(TotalProgress2 * 10000 div TotalSize2);