Bring a large pot of salted water to a boil. Cook the pasta according to package directions until al dente. Before draining, reserve about 1 cup of the pasta water.
While the pasta cooks, heat the olive oil in a large skillet or pan over medium-high heat. Add the cubed halloumi and cook, turning occasionally, for about 3 minutes until golden brown on most sides. Transfer the halloumi to a plate.
Add the halved cherry tomatoes to the same skillet. Cook for 1 to 2 minutes, stirring, until they just begin to soften. Transfer them to the plate with the halloumi.
Reduce the heat to medium and add the zucchini and garlic to the skillet. Cook, stirring frequently, for 2 to 3 minutes until the zucchini is slightly tender.
Pour in the canned diced tomatoes and add the olives and dried oregano. Bring the sauce to a simmer, then cover and cook for 10 minutes, stirring occasionally.
Drain the pasta and add it directly to the skillet with the sauce. Add the cooked halloumi, cherry tomatoes, and fresh parsley.
Toss everything together until well combined. If the sauce is too thick, add a splash of the reserved pasta water until it reaches your desired consistency. Serve immediately.