In a medium mixing bowl, combine the crushed pineapple, lime zest, fresh lime juice, minced garlic, apple cider vinegar, chili powder, cumin, kosher salt, minced jalapeño, Worcestershire sauce, fresh cilantro, and ¼ of the sliced red onion. Add the chicken strips, turning them in the marinade until evenly coated. Allow the chicken to marinate at room temperature for at least 30 minutes, or cover and refrigerate for up to 4 hours for more intense flavor.

Heat 2 tablespoons of vegetable oil in a large cast-iron skillet over medium-high heat. Once the oil begins to shimmer, work in batches to add the marinated chicken in a single layer. Stir occasionally and cook until the chicken is fully cooked through, about 15 minutes. Transfer the cooked chicken to a plate and set aside.

In the same skillet, increase the heat to high and add the remaining 2 tablespoons of vegetable oil. When the oil begins to smoke lightly, add the thinly sliced bell peppers along with the remaining onion. Sauté the vegetables, stirring occasionally, until they are browned and tender, approximately 5 minutes. Return the chicken to the skillet and toss to combine with the vegetables.

Serve the fajita filling in warmed tortillas, accompanied by lime wedges, fresh cilantro, avocado slices, and queso fresco if desired.