Slice the chicken breast into even bite-sized pieces and season with the sea salt, black pepper, and dried oregano.
Dice the zucchini, red bell pepper, and red onion into uniform half-inch pieces, and finely mince the garlic cloves.
Heat the olive oil in a large stainless steel or cast iron skillet over medium-high heat until the oil is shimmering.
Add the seasoned chicken to the skillet in a single layer and sear for 5-6 minutes, turning occasionally, until golden brown and cooked through.
Remove the chicken from the pan and set it aside on a plate.
In the same skillet, add the onion, bell pepper, and zucchini, sautéing for 4-5 minutes until the vegetables are tender yet retain a slight crunch.
Stir in the minced garlic and cook for an additional 60 seconds until fragrant.
Return the cooked chicken to the skillet, drizzle with fresh lemon juice, and toss everything together for 1 minute to combine the flavors before serving.