You can't "hide" a cell the way you can hide a row or column, but you can
make it appear blank.
Option 1: Wrap your formula in an if statement like this...
=IF(SUM(data)=0,"",SUM(data))
Option 2: Make a custom number format that outputs nothing for zero values.
highlight the cells in question
select format->cells->number tab
under "category" click on "custom"
enter the following under "type"
General;-General;;@