When I delete the C5 data validation, the zero still showing. It should be blank when the C5 is being deleted.
Can you please check to see what I did wrong.
RDEXCEL2020
How do You delete the C5 data validation?
If You mean by [Reset], then that won't delete it!
... and those 'zero's comes from Your formulas.
When I delete or reset the C5, it should leave blank the cells G12, AN12, AN15, AR15, D17 which there is a formula.
e.g.
=IFERROR(LOOKUP(2,1/(Reference=$C5),ITEM!$C$1:$C$7),"")