SPOILER WARNING: This article contains major spoilers for "Trajectory," the latest episode of "The Flash."
In "Trajectory," the latest episode of "The Flash," Team Flash uncovered a few uncomfortable truths about Zoom: that Jay was Zoom the whole time, and that he's dying.
Cisco spent the episode accidentally Vibing whenever he stood near Jay Garrick's helmet, which the team had placed in a glass case in his memory, having seen him "die" only two episodes prior. At the end of the episode, he followed through on his visions, and watched Jay -- who, as we now know, is actually Hunter Zolomon -- unmask himself. Horrified at this revelation, Barry sped out of the room, only to scream his frustration where no one else could hear him.
Barry's encounters with Trajectory also revealed that Zoom is dying. Trajectory was addicted to Velocity-9, a formula Caitlin invented to help give Jay his speed back. During their final fight, she overdosed on the drug, which caused her yellow lightning turn blue, just like Zoom's -- just before she completely disintegrated. When he recounted this to the team, they were able to piece together that the blue lightning is a side effect of V-9 usage, which means Zoom has been using it as a speed enhancer. However, V-9 causes cell degeneration, and that means Zoom is dying -- which would explain why he needs Barry's speed.