It is mostly my own labbing and experience playing Jokers (although a majority online). Although I am still winning most the time, I can see how Joker footsis and spacing in the neurtral are very good against Zod. Corner is a gg against Zod with no safe wakeups and your jump ins are really good at controling space and blowing up his backdash.
The hardest part for Joker is definitely finding a way to reduce the amount of trait summons I get. I am winning because people still have lots of difficulty defending against trait just in general (online doesn't help). Basically I gets lots of free traits which almost always mean free 40% combos against the untrained. It still needs a lot of exploring before a 7-3 or 6-4 could be decreed
I do have to say I agree with a lot of what you are saying definitely. However, I've played this MU way to much to know that trait isn't the only thing that beats Joker. Zod overall can just zone Joker out. I'm just going to discuss why I definitely feel its 7-3 based on the tools Zod has and how I've seen them used in this MU.
Zod has 3 different speeds for Zod balls which you can't tell the speed unless the ball comes out first. The start up is rather slow and can be punished by revolver but depending on the balls speed its most likely an unfavorable trade for Joker due to the ball on contact putting Joker in the air for a free trait summon.
IA balls are also another gamble yet again for Joker, except you need to read the IA ball to trade and most Zod players like Dave do fast IA balls so its unfavorable trade yet again for Joker because its a free trait summon. On reaction, you can punish IA balls but its more or less a read because they are safe way to get them on the screen.
Also the fact that Zod can get 2 balls on the screen at the same time depending on what Joker was doing and grants him either a free trait summon or continued spacing and meter building which brings me to my next point.
Side arm, particularly MB side arm can keep Joker in check and is a great way of keeping him away and from dashing in, meaning Joker legitimately has to inch his way in which leads to my point. Once Joker has Zods respect, which he will have fairly quickly because one mess up and traits out, Zod balls and the MB heat vision shit really keeps Joker out and guarantees a trait call for Zod.
Example, IA ball is out. Joker can go for a revolver shot or duck under. Joker ducks under to avoid the hit and trait call and gets MB heat vision out instead and get a trait call anyway.
Now lets say Joker gets in, Zod will definitely have at least 1 bar of meter, definitely more but I'll just say 1 for now, Jokers neutral game sucks and has no reliable way of getting in which means pushblocking any hit he throws outs you back and the shit begins again.
I've played this MU so much and every High level Zod I've played pushblocks and the worst part is Joker can't do shit unless Joker had clear contact prior to the pushblock and bounce cancels through the pushblock for some damage but even then you spend 2 bars and your execution and follows ups have to be on point and flawless for you to keep going because one pushblock and thats it bro.
This MU is Zods MU the second he gets away and his backdash supports it. The only time Joker can fully punish Black Adams, I mean Zods backdash is if its on wake up and Joker is right on him. Otherwise Joker can get a gunshot in... thats it. This MU is way too easy for Zod due to the million ways he can get trait and on some levels doesnt need trait and Joker has nothing reliable to fall back on besides a full screen super and godlike blessing of a hitconfirm.
I'm not sure how many Joker players you've played or if you have the full MU experience at the time you played them but every Joker plays differently even though we all have different conclusions on this MU, we've all looked free due to Zods overall dominance with his tools and Joker just can barely compete. I definitely value and appreciate everything you've said though and I will definitely lab the MU again to see if I can come up with more options. Thanks man.