If you want to display the zero as blank you can go to Option dialog to uncheck the Show a zero cells that have zero value option and then the formula cells will keep blank untile the reference cells entered with values. The ISBLANK function returns TRUE if a cell is empty and FALSE if not. To use the ISBLANK you can revise the formula as follows.
VBA can either replace permanently a formula that created the blank cell or it can look at the contents of 1 cell and set another one to empty.
The first step is the enter something other than double quotes into our IF statement. If the input cell contains a space or a formula that returns an empty string it looks blank. For example you need to evaluate that if a cell is Blank the blank value otherwise return a value Delivered. Using option 3 changes it to blank again.