A new preference was added to allow you to control whether you want to display zero currency amounts in forms. 

Select the gear icon on the lower right of main command center window to open Preferences or select Setup then select Preferences>Reports & Forms and check or uncheck the preference for “Hide Zero Currency Amounts in Forms”.  

In build 33.x.1, based on user requests, we added zeros to line items on forms with no Amount.  In build 33.x.2 we added a new preference to give you control on whether to use it.