Salmon Tostadas with Zucchini-Radish Slaw

Stir together sour cream, lime zest, garlic, ground chipotle chile pepper, lime juice, and salt and pepper to taste. Toss together cabbage, zucchini, radishes, cilantro, jalapeño pepper, olive oil, lime juice, and salt and pepper to taste. Let stand 15 minutes. Flake salmon into pieces, discarding skin. Spread sour cream mixture over tostada shells, and top with salmon and cabbage mixture. Cut avocado into 6 wedges. Top tostadas with avocado wedges; serve immediately.