While the past papers (Greenbooks) are for practice, you need a core textbook for theory. ZIMSEC syllabi are adapted from the UK Cambridge system (CAIE), but with local context.
Mastering ZIMSEC A-Level Physics: Why the Blue Book is Your Best Study Companion
The Blue Book has ~50 questions per topic. Do not do them all.
(like PhET) to visualize abstract concepts like Wave Interference or Quantum Physics.