When writing an essay, research paper or any other formal document, it is important to know a variety of synonyms for common phrases like "in combination with." Some alternatives you can use instead include: together with, coupled with, in conjunction with, along with, concurrently with, and jointly with. These phrases emphasize that two or more things are working together to achieve a certain result. Additionally, you can also consider using phrases like "in tandem with", "hand in hand with", or "as well as" to convey the same idea. Using these synonyms can help you avoid repeating the same phrase throughout your writing, resulting in a more varied and engaging piece of work.