8x8 Zigzag Sudoku Snack

Normal irregular 8x8 Sudoku rules apply, i.e. each row, column and region has to contain the digits from 1 to 8. On the main diagonals digits do not repeat. Digits on a grey line form a palindrome, i.e. they read the same forward and backward. Digits on an arrow sum to the digit in the circle from which the arrow emerges. Digits on a marked diagonal sum to the little killer clue outside the grid. (If there is no conflict with other rules, digits on such a diagonal may repeat.)