Users working in a shared workbook save more than data. They save their personal druthers, such as the zoom factor. You can avoid this problem by standardizing the zoom factor using a macro.
Private Sub Workbook_Open()
ActiveWindow.Zoom = 100
End SubBe sure to save the workbook after adding the macro. You can replace 100 with whatever zoom factor is the most common. Regardless of the setting each user saves with the workbook, Excel will reset it to 100 (or whatever zoom factor you specify in the macro) each time a user opens the workbook. You can use this technique to standardize a number of common environmental settings.