For example:

extent := GisNoWorld ;
shp := ll.FindFirst( extent, 'ID=1' )
if Assigned( shp ) then begin  
  extent := GisMaxExtent( extent, shp.ProjectedExtent ) ;
  GIS.VisibleExtent := extent ;
  GIS.Zoom := GIS.Zoom / 2 ;
end ; 

Note:
TGIS_Shape.Extent and TGIS_Shape.ProjectedExtent are similar. The main difference between them is the first provides extent in the layer coordinate system, whereas the second provides extent already in the viewer coordinate system.