1. Finely dice bell peppers. Peel and finely dice onion. Slice zucchini and squash and then cut them into half rounds. Finely chop parsley.
2. Peel and devein shrimp. Slice andouille sausage.
3. Toss the shrimp with one third of the olive oil and one half of the cajun seasoning. Set aside.
4. Set a large skillet over medium heat and add the andouille sausage.
5. Cook, stirring occasionally, until the sausage is browned, approximately 4-5 minutes. Transfer sausage to a plate and set aside.
6. Add 1/3 of the olive oil to the skillet, along with the shrimp. Spread the shrimp into a single layer without overcrowding.
7. Cook, stirring once, just until the shrimp are opaque and start to curl, approximately 2 minutes. Do not overcook. Transfer shrimp to the plate with the sausage.
8. Add remaining oil to the skillet, along with the onion, garlic, and bell pepper.
9. Sprinkle with additional cajun seasoning, to taste, and stir to combine.
10. Cook, stirring frequently, until the vegetables soften and develop some color, approximately 4-5 minutes.
11. Add the yellow squash and zucchini to the skillet and cook, stirring frequently, just until browned and crisp-tender, approximately 2-3 minutes.
12. Remove from heat and stir in the andouille sausage, shrimp, and fresh parsley. Stir to combine and serve immediately. Enjoy!