How to Make It
Process oil, chipotles, vinegar, sugar, and 1 teaspoon cumin in blender until smooth. Add to a bowl with fish. Chill 15 minutes.
Heat a grill pan coated with cooking spray over high. Coat squashes and serranos with cooking spray, 1/2 teaspoon salt, and remaining 1 teaspoon cumin. Grill vegetables until charred, 2 minutes per side for squashes and about 5 minutes for serranos. Roughly chop vegetables.
Recoat pan with cooking spray. Cook fish over high until flaky, 2 to 3 minutes per side. Cut into chunks. Season with remaining 1/4 teaspoon salt.
Stir together sour cream and lime juice. Divide fish and vegetables among tortillas. Top evenly with pico de gallo and sour cream mixture.