if function with error checking

Hello

My file looks like this:

Column
A - number of pieces (manual input)
B - x dimension of area (manual input)
C - y dimension of area (manual input)
D - area based on B and C (formula = B*C)
E - irregular area (manual input, if area is not rectangle)

F- solve for density number (pcs/area)

my first code, assuming ROW 1

=IF(D1=0,A1/E1,A1/D1)

this code is ok but it will give DIV/0 error if B or C is blank.
I want Div/0 be blank/zero

my 2nd code does not work

=IF(D1=0,A1/E1,IF(ISERROR(A1/D1),"",(A1/D1)))

TIA