I don’t know if this is new to anyone, but a video on YouTube confirmed that all damage boosting abilities stack.
Damage boost+Supercharger+Nanoboost yield 130% more damage.
But that’s not all. Zenyatta’s discord orb amplifies damage that is already amplified. It doesn’t simply add another 30%.
Example: Doomfist’s fully charged Rocket Punch(without wall impact) deals 100 damage. If you apply the boosts from damage boost, supercharger and nanoboost, he deals 130% more, resulting in 230 damage. If he also uses his boosted damage on an opponent that is discorded, you add 30% of the 230 damage he does with all the boosts already affecting it. Topping it off at 299 damage.
Conclusion: All damage boosting effects stacked yield 299% damage output or a multiplier of 2.99.
Look up: Overwatch MythBusters - DAMAGE BOOST STACKING - Plus Damage Resistance Stacking
On YouTube.
Edit: Or scroll down and hit the link provided by Prett.
Edit: I wanted to show how Discord orb works in tandem with other singlular damage boosts.
If we assume your damage is 100:
Damage boost + Discord = 169 damage. Adds 69% or a multiplier of 1.69.
Supercharger/Nanoboost + Discord= 195
Adds 95% or a mulitplier of 1.95