Shred chicken and add to a large bowl. Dice celery, halve grapes, slice green onions and chop pecans; add all to bowl with shredded chicken. Mix mayo, yogurt, chopped dill, salt and pepper into the chicken. Stir in 1 teaspoon of lemon zest and juice of the lemon.
Add an even amount of chicken salad to each tortilla. Wrap tightly and slice in half. Serve any extra grapes on the side.