PowerQuery: Can't Replace #DIV/0! with null

#DIV/0 and #N/A import as an error in Power Query and can not be distinguished from any other error.

So you can use the Query Editor options for handling error values:

replace error values via Transform - Replace Values - Replace Errors or

remove rows with errors via Home - Remove Rows - Remove Errors.

This works for the selected columns. In order to remove errors from the entire table, you can use the dropdown at the very upper left corner of the table, and then select Remove Errors (close to the bottom of the list).

If you want to replace errors in all columns then you must select all columns first and then use the option on the Transform tab.