Zenyatta is unplayable for me. Don't know why, but I just can't use him..feels bad lol. I like the design so I wish I was good enough.
You just gotta think of zenyatta similar to mercy except his range on healing is line of sight. And at minimum you heal for 3 seconds so 120 hp, which isn't bad for the range and lack of cooldown. It's also only 30 hp less than a mercy would heal in the same time, except mercy needs to get much closer and thus more vulnerable.
Orb of discord is where he really shines. Zero cooldown that lasts at least 3 seconds, more than enough time to kill anyone in the game generally speaking. Makes him hit about as hard as mccree regardless of range and his clip is like 20-25 shots rather than 6.
And his ult is really top notch if you need to deal with a lot of midrange defenders imo. 100hp per second iirc.
The challenge of zenyatta is balancing both the orbs while DPSing and maintaining solid positioning. There are good reasons why he isn't a heavily picked support, but he does work when played well. Against heavy tank comps, I'd rather a mercy switch to zenyatta (usually also running a lucio or second support already btw) rather than switch to accommodate a surprise extra winston or something like that.
Winston works pretty well too against her.
If winston ever kills tracer, it's probably because the tracer made a mistake. It's just way too easy to stay out of his range while pouring damage into his huge hit box. If he gets the drop on tracer, recall ensures getting back to full clip plus full health in a single move, often also putting her out of range in a single sweep.