Diagonal Sudoku Help

Diagonal sudoku adds one or two diagonals to the grid. Digits on the diagonal(s) must be unique.

Diagonal going from top left corner to bottom right corner is called negative diagonal (it is going down if we are looking at the grid from left to right). The other diagonal is called positive diagonal.

Diagonal Sudoku Solving Strategies

Each diagonal is a house same as rows, columns and 3x3 boxes, this means pairs, triples and quads can be applied to diagonals.

On grid above 2 and 3 can be placed in only two cells on negative diagonal (R3C3 and R4C4). Which means we can place 3 and 9.