Chelsea’s first-half efforts paid off when Raheem Sterling, formerly of City, found the far corner with a clinical finish three minutes before halftime.
A few minutes before halftime, Saka, from the penalty spot, doubled Arsenal’s lead before scoring his second in the game.
The Gunners broke through West Ham defence, netting four of their six goals within 15 minutes.
With Burnley’s persistent efforts, they managed their first goal against City in nine games during stoppage time.
In the second half, Liverpool improved, as Jürgen Klopp moved Núñez to the left side.
With Thursday night’s defeat, Arsenal are now behind Liverpool with two points, having garnered 40 points in 19 games this season.
Brazilian striker Gabriel Jesus opened the scoring for the Gunners with a header from a corner in the 53rd minute.
Bayern Munich, with 13 points, have already been confirmed as the runaway winners of Group A.
With Saturday’s win, Arsenal displaced City from the top spot, garnering 30 points in 13 games this season.
Zinchenko made it 3-1 with an improvised volley after Burnley failed to clear a corner.
