Place the numbers 1 to 9 once in each row, column, long diagonal
and 3x3 box. Obviously, the central yellow-coloured 3x3 box is common to both grids.
The number in the cage (or shaded area) represents the result of an arithmetical operation by its accompanying sign. For example, 4÷ in a two-celled cage means that it contains either 8 and 2 or 4 and 1 (in any order).
Unlike Killer Sudoku, the same number may appear more than once in a cage. So, 28x in a cage which overlaps the 3x3 grids may contain two 2s and a 7.
Once again, I wish to thank brianjn most sincerely for his continued support. He converted my black and white Excel image to a coloured one in 'jpg' format.
Acknowledgement to Peter at sudexel.com for beta testing the puzzle.
(In reply to Hint
Welcome back, nikki!
When making puzzles of this type, I try to provide clues which feature mainly the odd numbers. In this way, there is little (or no) room for misinterpretation. A couple of months ago, I learned a hard lesson, by wrongly assuming that a couple of factors were 2 and 9. After several failed attempts at the puzzle, I finally realised that the factors were 3 and 6!
Congratulations on your endurance with the walk-through solution.