Don't use thin pretzels in this recipe--they'll make the cakes too salty.
Break pretzels into pieces; pulse in a food processor until finely ground. (You should have 1/2 cup.)
In a medium bowl, combine mayonnaise, egg, dill, scallions, and lemon zest. Fold in ground pretzels and salmon until just combined. Cover and refrigerate until firm, about 30 minutes. Using a 1/4 cup measure, form mixture into 8 cakes, each about 1/2 inch thick.
Heat a large skillet over medium-high. Add 1 tablespoon oil. Cook 4 cakes, flipping once, until golden brown and crisp, about 3 minutes a side. Repeat with remaining oil and cakes. Sprinkle with dill and serve, with lemon wedges.