Unfortunately I cannot tell you whether you will receive a gold medal or Rs. 5000 solely on a zonal rank as the criteria for awarding search rewards can vary from school to school. Your school might have its own criteria for awarding medals and scholarships based on the academic performance. It's best to check with the School authorities or if the competition is conducted by a state Education Board then you can check with the state. department whether they will provide you the prize or not as they might have different criteria.Similarity if the competition is national level then you can check. with the national competition board or visit their official website to check the prize criteria