I recommend the Saxon Math books. Although you many not think you need it, it is best to start at the 4/5 level and work through each book until college level calculus and physics. I have done this and now I do calculus and physics problems for fun. It is far more engaging than Sudoku.
I was thinking about it more for my son. He graduated from high school this year, but trying to learn calculus via Zoom did not work out very well for him. He is taking some time off from school right now, but he will probably need to re-take calculus.
Maybe he should work on Saxon pre-calculus before re-taking calculus?