Hopefully injuries won't be a problem for him in the future, but I am not too worried about a torn meniscus. I have had a few of these over the years. You can actually typically continue playing (whatever sport), but things really flare up that night and the next morning where you can't bend or unbend your knee. Never waited a full 6-8 weeks (more like 2) to get back to what I was doing, but I also don't play professional sports and they probably were never that serious. I imagine the arthroscopic surgery was more precautionary.
Zion should be fine in a few weeks and should wow us with his athleticism soon enough. Having an awkward thing like a meniscus tear isn't a cause for alarm - just an unfortunate circumstance that will delay his rookie season. Looking forward to his return.