Arrange grated zucchini and squash on a large baking pan; sprinkle with 1 teaspoon kosher salt. Let vegetables rest 15 minutes. Drain well, pressing between paper towels, and set aside.
Heat 1 teaspoon canola oil in a small sauté pan, and sauté leek 3 minutes or until soft. Set aside.
Grate potatoes, and press between paper towels to remove excess water. Place potatoes in a large bowl; add zucchini, squash, leek, remaining 1/2 teaspoon salt, and 1/4 teaspoon white pepper, and stir gently. Add red onion and next 6 ingredients, stirring gently to combine.
Heat 2 to 4 tablespoons oil in a large nonstick skillet over medium-high heat. Spoon heaping tablespoons of latke mixture, squeeze out extra liquid, and form into flat patties. Fry latkes, in batches, 1 to 1 1/2 minutes on each side or until golden. Remove from skillet, and drain on paper towels. Top each with a piece of smoked salmon, a dollop of sour cream, and caviar. Serve immediately.