Hello, long time stalker, just thought I could contribute a little...
66A+B on block, 2nd hit can't be stepped/interrupted but can be jGed/GIed. From there the opponent is unlikely to move, which grants additional options.
66[A+B] slight hold leaves ZWEI at more advantage on block, provided the opponent didn't step EIN. 66B after 66[A+B] slight hold cannot be stepped/interrupted, and GI may be impossible depending on the duration of delay. I find it optimal to release EIN just after the 1st hit is blocked. The "string" breaks guard in about 4.5, provides a decent spacing afterwards, negates EIN cooldown and trigger the opponent to try to step/interrupt (which 66A+B beats) or GI on reaction(I haven't had too much success GIing 66A+B and 66[A+B] simultaneously on reaction myself) before EIN is blocked. If EIN is blocked and the opponent is conditioned to be forced to block 66B, it gives potential for post EIN on block run in mixups/KF B.
If the opponent is bent on holding their ground with GI on reaction against EIN to potentially beat both 66A+B and 66[A+B] slight hold shenanigans, 66[A+B] full hold becomes another option. 66[A+B] full hold run in 2K on hit forces the opponent to block the incoming EIN for a similar advantage situation as above: post 66[A+B] full hold run in 2K, 66B cannot be stepped and gives potential for mixups. Even if 2K is blocked, it can't be directly punished and EIN is still unsteppable; it only loses to post 2K on block GI.
You can also opt for 66[A+B] + grab shenanigans to beat GI. Its possible to execute 66[A+B] full hold run in grab for a force grab situation if the opponent hasn't already stepped out of the way, but execution can make it less accessible. I personally go for 66[A+B] full hold 9G grab as it entirely takes away the execution barrier. There's no way to duck the grab unless the opponent ducks before EIN hits, which means they get launched. After grab on whiff, combos for 51 damage(can't be aerial controlled as far as I've tested). If the opponent tries to GI EIN while ZWEI is already in the grab animation, EIN will go through the GI and the opponent just wasted meter.
The GI negation extends further from just this setup, as GI negation works so long as ZWEI is in grab animation. For example, 1B at far ranges might trigger nightmare to opt for CE. So in this position, ZWEI can counter it with jG or whiffed grab as EIN is released.
66A+B on grounded hit, is usually landed during combos or okizeme. Additional options work similarly to 66A+B on block, but significantly safer even on wrong guesses.
Depending on the extent of delay on 66[A+B] slight hold on grounded hit, a ukemi-ing opponent is either still stuck on the ground, or they are launched by EIN. Ideally, this gives an opportunity for more damage in combos. For example, B+K 4B BE, 66[A+B] slight hold run in 1K works if the opponent is still grounded. This discourages opponents from ukemi-ing from 66A+B combos as a whole. Unfortunately it is character specific, most characters can ukemi to ZWEI's right if 66[A+B] is delayed for a launch, but the fundamental idea is to discourage the opponent from back ukemi-ing which will be elaborated later.
Without ukemi, the opponent is mostly limited to holding G, rolling, or wakeup attacks. 66[A+B] full hold is the main tool here.
66[A+B] + grab shenanigans on grounded hit grants similar rewards as it does with on block, but its a lot easier to land and a lot safer. Once again its possible to go for 66[A+B] into a well timed EIN release and grab for a quick way to beat holding G, but it is punished heavily by rolling. Over here there are two benefits to going for 66[A+B] full hold 9G grab: there is no execution barrier and 9G screws up rolling. A commit roll with no intentions to guard by the opponent will result in them rolling back into EIN (although there are character specific instances where the opponent can commit roll into EIN and not be hit, but ZWEI is still safe), and against rolling G, ZWEI is still safe as the opponent must block EIN upon waking up. 66[A+B] + grab shenanigans is only punished by wakeup attacks.
Wakeup attacks can be punished or neutralised, by delayed 2K post 66[A+B] full hold on grounded hit, along with holding G, rolling and side ukemi-ing. If 2K is not delayed, it'll typically whiff against rolling to ZWEI's right. I generally input delayed 2K as 82K, so its easier to judge when ZWEI has recovered from 66[A+B] animation for better timing. Against commit roll, delayed 2K EIN run in 2K becomes a grounded combo. For comparison:
B+K 4B BE 66[A+B] slight delay run in 1K does 87 damage
B+K 4B BE 66[A+B] full delay delayed 2K run in 2K does 67 +46 = 113 damage
Unfortunately EIN does not always combo after the delayed 2K on grounded hit (rolling direction and character specific).
Holding G, rolling G and side ukemi-ing will allow opponents to avoid getting comboed, but put them in a similar situation to the previous 2K setup; the opponent is forced to block EIN and 66B/deal with potential mixups unless they blocked 2K and GI. Delayed 2K is only punished by back ukemi (which 66[A+B] slight delay beats), probably making this option the safest and easiest to land.
Rolling G is probably the most specific response from opponents once they figure out they can avoid any ukemi traps, the grab shenanigans and getting ground comboed from 66[A+B] on grounded hit. It can be observed from the delayed 2K setup (by seeing if they have gotten up to block EIN in time). From here 66[A+B] full hold KF B cannot be avoided in time.
Not sure if I missed anything... Hopefully I'm not repeating too much of old tech. -.-
Okay bye. :P
