As a seasoned Python developer with extensive experience in backend development and software engineering, I can confidently undertake this project and deliver it to your utmost satisfaction. My in-depth knowledge of frameworks like Flask and Django, which you've mentioned in your project description, makes me adept at developing powerful and efficient systems - precisely what you need for a Windows-based Python GUI app.
Moreover, my fluency in frontend technologies like React.js will be valuable for delivering a user-friendly and visually appealing interface, while my familiarity with databases such as MySQL and MongoDB will ensure seamless integration with existing APIs. Additionally, my proficiency in Node.js means that I am equipped to handle server-side requirements with swiftness and scalability - as the situation demands.
Finally, my hawk-eyed attention to detail allows me to thrive even in complex projects - making sure they are not just functioning but also optimised. Trusting me with this project would mean availing the benefits of an astute problem-solver who's dedicated to turning your project into a success. I'm confident that my skills together with my passion for development make me the best candidate for this project. Let's get started!