Hi ak2022,
740/750 is a great start my friend. Regarding verbal, as long as you continue practicing all aspects of verbal, I think you can maintain your verbal skills. Regarding how to improve in quant, you have to go through GMAT quant carefully to find your exact weaknesses, fill gaps in your knowledge, and strengthen your skills. The overall process will be to learn all about how to answer question types with which you currently aren't very comfortable and do dozens of practice questions category by category, basically driving up your score point by point.
For example, if you find that you are not strong in answering Number Properties questions, then carefully review the conceptual underpinnings of how to answer Number Properties questions and practice by answering 50 or more questions just from Number Properties: LCM, GCF, units digit patterns, divisibility, remainders, etc. When you are working on learning to answer questions of a particular type, start off taking your time, and then seek to speed up as you get more comfortable answering questions of that type. As you do such practice, do a thorough analysis of each question that you don't get right. If you got a remainder question wrong, ask yourself why. Did you make a careless mistake? Did you not properly apply the remainder formula? Was there a concept you did not understand in the question? By carefully analyzing your mistakes, you will be able to efficiently fix your weaknesses and in turn improve your GMAT quant skills. Number Properties is just one example; follow this process for all quant topics.
Each time you strengthen your understanding of a topic and your skill in answering questions of a particular type, you increase your odds of hitting your score goal. You know that there are types of questions that you are happy to see and types that you would rather not see, and types of questions that you take a long time to answer correctly. Learn to more effectively answer the types of questions that you would rather not see, and make them into your favorite types. Learn to correctly answer in two minutes or less questions that you currently take five minutes to answer. By finding, say, a dozen weaker quant areas and turning them into strong areas, you will make great progress toward hitting your quant score goal. If a dozen areas turn out not to be enough, strengthen some more areas.
So, work on accuracy and generally finding correct answers, work on specific weaker areas one by one to make them strong areas, and when you take a practice GMAT or the real thing, take all the time per question available to do your absolute best to get right answers consistently. The GMAT is essentially a game of seeing how many right answers you can get in the time allotted. Approach the test with that conception in mind, and focus intently on the question in front of you with one goal in mind: getting a CORRECT answer.
In order to follow the path described above, you may need some new quant materials, so take a look at the GMAT Club reviews for the
best quant courses.
You also may find it helpful to read this article about
How To Increase Your GMAT Quant Score.
Feel free to reach out with further questions.