Author here,
I will be skipping the Zero arc as there is nothing there that will really impact this book. There will be talk about his presence being there and the consequences of it but I won't write about it any further. The first arcs of JJK he won't have much of a presence so it will be more of a straight jump into the Shibuya arc.
That's where I will start really changing the timeline and events. Things won't go the same way, at least not exactly and expect some more people dying.
Happy thoughts happy life.