This is the OUTLINE for what you need to do. You will need to add the relevant code for tables and shapes and declare the variables for the table
Sub ZeroMargins()
Dim oshp As Shape
Dim osld As Slide
Dim otbl As Table
For Each osld In ActivePresentation.Slides
For Each oshp In osld.Shapes
If oshp.HasTable Then
Set otbl = oshp.Table
With otbl
' put the table code here
End With
Else
If oshp.HasTextFrame Then
With oshp.TextFrame
' code for shapes goes here
End With
End If
End If
Next oshp
Next osld
End Sub