Grade School Multiplication

An educational software company, All Computer Math (ACM), has a section on multiplication of integers. They want to display calculations in the traditional grade school format, like the following computation of 432 \times 5678:

  432
× 5678
-------
 3456
 3024
 2592
2160
-------
2452896

Note that the final product is printed without any leading spaces, but leading spaces are needed on some other lines to maintain alignment. According to our regional rules, there should never be any lines with trailing white space. The lines of dashes have a length matching the final product.

As a special case, when one of the digits in the second operand is a zero, it generates a single $0$ in the partial answers and the next partial result should be on the same line, not the next line down. For example, consider the product 200001 \times 90040:

  200001
× 90040
-----------
  8000040
180000900
-----------
18008090040

The rightmost digit of the second operand is $0$, placing a $0$ in the rightmost column of the first partial product. Instead of moving to a new line, the partial product of 4 \times 200001 is placed on the same line as that $0$. The third and fourth least-significant digits of the second operand are also zeros, each resulting in a $0$ in the second partial product on the same line as 9 \times 200001.

In the final special case, if there is only one line in the partial answer, it is the full answer so there is no need to compute a sum. For example, 246 \times 70 would be formatted as:

  246
×  70
-----
17220

Your job is to generate such displays for these multiplications.