Pat steak cubes dry with paper towels and season evenly with salt and black pepper.
Heat olive oil and 1 tablespoon of butter in a large skillet over medium-high heat until the fat is shimmering.
Add steak bites in a single layer, working in batches if necessary to avoid overcrowding, and sear for 2 minutes per side until browned; transfer steak to a plate.
Reduce skillet heat to medium and add the remaining 3 tablespoons of butter.
Add the zucchini half-moons to the skillet and sauté for 4 to 5 minutes until tender-crisp and slightly golden on the edges.
Add the minced garlic, dried oregano, and red pepper flakes to the pan; cook for 60 seconds until fragrant.
Return the seared steak bites and any accumulated juices to the skillet, tossing for 1 minute to coat thoroughly in the garlic butter.
Remove the pan from heat, stir in fresh lemon juice, and garnish with chopped parsley before serving.