The most common version is "O Level Chemistry for Zimbabwe" by G. B. Chitumba or the "New Horizon Chemistry" by D. J. Simbi . Check the cover – if it’s green and has a test tube on it, you have the right one.
The is the digital Holy Grail for modern students. However, spending weeks trying to find a clean, legal, free PDF is often a waste of valuable study time. Zimsec O Level Chemistry Green Book Pdf