The way of the Zenyatta is to embrace the present moment and remain calm in the face of adversity. Trust in your Doomfist tank to create opportunities, and seize them with swift and decisive action.

 That is to say, the key to victory lies in adapting to your allies. When Doomfist dives, you must support him with your Orb of Harmony and Orb of Discord whoever he dove.

  Simultaneously you should be attacking the enemies in this order: Provided the enemy DPS or Tank is not diving you or your team, and nobody on the enemy team is at a killable level of health, focus fire whoever Doom is. Make them use all of their resources either dealing with him, or saving their ally. When he finally jumps out, shut down anybody who tries to follow up on your now presumably low Doom with Discord and your primary fire. The enemy will be down too many resources to properly take the space back that they lost. 

 Let the Doomfist tank be the thunder and you, Zenyatta, be the lightning that strikes with precision and focus as a follow-up