Preheat your oven to 400°F (200°C).
Rinse the quinoa under cold water, then combine it with 0.5 cup water in a small saucepan; bring to a boil, reduce heat to low, cover, and simmer for 15 minutes.
Slice the zucchini into half-inch thick rounds and toss them in a bowl with 0.5 tablespoon of olive oil, a pinch of sea salt, and black pepper.
Spread the zucchini in a single layer on a parchment-lined baking sheet and roast for 15-20 minutes until tender and slightly browned.
Season the chicken breast evenly on both sides with the dried oregano, remaining sea salt, and black pepper.
Heat the remaining 0.5 tablespoon of olive oil in a skillet over medium-high heat and sear the chicken for 6-7 minutes per side until fully cooked through.
Add the minced garlic, lemon juice, and lemon zest to the skillet during the last 2 minutes of cooking, spooning the juices over the chicken.
Remove the chicken from the heat to rest for 3 minutes, then fluff the quinoa with a fork and serve alongside the roasted zucchini.