Simplify the following text for a Grade 8 native English-speaking person.
Original: If either of the vectors being multiplied is zero or the vectors are parallel then their cross product is zero . More generally , the magnitude of the product equals the area of a parallelogram with the vectors for sides ; in particular for perpendicular vectors this is a rectangle and the magnitude of the product is the product of their lengths .
Simplified: The cross product of two vectors is always perpendicular to both of the vectors which were `` crossed '' .