Format FRS report to show '-' for zero values, but export to excel with value of '0'

Summary: FRS report is showing correctly on the screen with zero values displaying as '-', but when the report is exported to excel the underlying cell value is also '-' and we need it to export as '0'. All of the conditional formatting I try is also changing the display to 0 and not just the underlying data.

Content (please ensure you mask any confidential information):

We want the display to show the '-' on the screen, but the value where the red arrow is to actually be '0'

This is how we want to see the zero values