For me the kickoff (zero) session should have heavy coop elements - we talk about my GM style, the world we’re going to play in, what each player would like to see in the game, what things they do NOT want see, talk about safety (X-card, lines, veils, etc), and the like.
For our current 5E game we built out the play area using The Quiet Year a very cool GM’less map building game easily used for world building if you hack it a little. I took everything we did in TQY and expanded it some with my own ideas which I sent to the players as we started playing.
I like to have each character connected to at least one other party member - usually I just go in a circle and ask each PC to make a connection with the PC on their left (or right if I’m feeling like it). I have done the Dresden Files style connections where you “guest star” in other PCs backstory - it uses a 1 thru 5 phase system to create character backstories… very cool though probably a bit much of D&D/ICRPG.