In a large wok or pot, heat the oil over medium-high heat. When hot, add the sliced flank steak, season with salt, and cook, stirring occasionally. When the steak is browned all over, transfer to a plate and set aside.
Return the wok or pot to medium-high heat. Add the garlic and curry paste and stir for 1-2 mins until fragrant. Add 1.5 cans of the coconut milk, lime juice, soy sauce, fish sauce, and broccoli. Bring to a boil, then reduce heat to medium-low to simmer. Add the red bell pepper and zucchini, and simmer until the vegetables are just tender, about 6-8 minutes. Stir in the remaining coconut milk.
Serve the curry over the rice, topped with the steak, basil leaves, and red finger peppers (if using), and lime wedges.