Selena Gomez, Demi Lovato, The Weeknd, Calvin Harris, 5 Seconds of Summer, Nick Jonas, Fifth Harmony, Zedd, Shawn Mendes, Fetty Wap, Tove Lo, Charlie Puth, Hailee Steinfeld and more: See photos from Z100’s Jingle Ball on Friday, Dec. 11, 2015, at Madison Square Garden in Manhattan.