Have Excel formulas that return 0, make the result blank

The normal way would be the IF statement, though simpler than your example:

=IF(INDEX(a,b,c),INDEX(a,b,c),"")

No need to do gyrations with the formula, since zero values trigger the false condition.

I am not sure it works with all type of data but the only solution I found for the moment is to test if index returns blank:

=IF(ISBLANK(INDEX(a,b,c)),"",INDEX(a,b,c))

The formula

=IF(INDEX(a,b,c),INDEX(a,b,c),"")

does not work with text

You can create your own user defined functions in a module within Excel such as (from memory, so may need some debugging, and the syntax may vary among Excel versions as well):

Public Function ZeroToBlank (x As Integer) As String
    If x = 0 then
        ZeroToBlank = ""
    Else
        ZeroToBlank = CStr(x)
    End If
End Function

You can then simply insert =ZeroToBlank (Index (a,b,c)) into your cell.

There's a nice tutorial on just this subject here.

The basic steps are:

• Open the VB editor within Excel by using Tools -> Macro -> Visual Basic Editor.
• Create a new module with Insert -> Module.
• Enter the above function into that module.
• In the cells where you want to call that function, enter the formula
       =ZeroToBlank (<<whatever>>)
  where <<whatever>> is the value you wish to use blank for if it's zero.
• Note that this function returns a string so, if you want it to look like a number, you may want to right justify the cells.

Note that there may be minor variations depending on which version of Excel you have. My version of Excel is 2002 which admittedly is pretty old, but it still does everything I need of it.