Earth 0 Timeline
2012- Oliver Queen becomes Green Arrow. Barry Allen gets hit by lightning. Roy trains to be Oliver's sidekick.
Oliver runs into his old friend Hal Jordan who is the Green Lantern.
2013 – Barry Allen becomes the Flash. Roy becomes Arsenal. Thea Learns Oliver's a hero. Sarah Lance is the Black Canary.
Flash and Green arrow work together to help Hawkman and Hawkgirl fight Vandal Savage. John Diggle joins the Suicide Squad for a mission.
2014- The Justice League is formed. Sarah Lance is killed. Laurel becomes the New Black Canary. Thea becomes Speedy.
Ray Palmer becomes the Atom. Flash meets Supergirl. The Dominators invade Earth.
Green arrow dies. The Justice League disbands. Roy Harper becomes the New Green Arrow. Flash defeats Zoom and goes back in time creating Future's End.
("A league of their own" "Battle for the Hood" "Speedy's Quest" "Arrowverse Ends")