Tieng Viet 123 (Vietnamese for beginners): Giáo trình tiếng Việt cho người nước ngoài (Vietnamese books for foreigners) Kindle Edition

I appreciate the effort all the teachers put in to create the book. It is very useful and easy to follow through. However, there is only one minor thing: It's quite hard to zoom in and out when I use kindle edition on my phone. I usually set the text size to large, but I couldn't do it with this kindle edition. I wish it could easily be adjustable as the demo pdf file.