If I understood you correctly, you want to hide the number 0 without deleting the formula on that cell.

I have tried it in excel 2007 (the newest version) and it should work on all versions of excel and windows.

Choose the cells you want, right click and then choose format cell. Choose the number tab and click on custom on the list you get. Type this into the text box: 0;-0;;@
 

This information also appears on a help page on the office support site.