Call the run Zoom75 subroutine when you open the file and run the Zoom100
subroutine when you close it.
Sub Zoom75()
Dim CurrWS As Worksheet
Dim WS As Worksheet
Set CurrWS = ActiveSheet
Application.ScreenUpdating = False
For Each WS In Worksheets
WS.Activate
ActiveWindow.Zoom = 75
Next
CurrWS.Activate
Application.ScreenUpdating = False
End Sub
Sub Zoom100()
Dim CurrWS As Worksheet
Dim WS As Worksheet
Set CurrWS = ActiveSheet
Application.ScreenUpdating = False
For Each WS In Worksheets
WS.Activate
ActiveWindow.Zoom = 100
Next
CurrWS.Activate
Application.ScreenUpdating = False
End Sub