My view/theory on the vfx process in ZSJL:

Zack is known for mixing practical and special affects a lot ehich enhances his vfx shots. Given that he already had many shots completed in his 2hr 20 min og theatrical release for JL back in 2017, but the problem is Zack was forced..

...to compromise by removing/vfxing elements intended for specific scenes/shots that were "tOo sCaRy" suxh as steppenwolf's spiky design etc. Bloggers would visit the editing room somewhat commandeer the editing process hindering it

Now Zack has full control, no compromise...

...So Zack decided to do a full restoration of his vision:

Gather all the scenes he needs (and shoot the additional photography for 1 extra scene) 4hr JL film.

Complete unfinished vfx shots/rework already completed shots...

...Color correcting scenes and restoring scenes that are "too violent"

All amounting to 2800+ VFX SHOTS in the entire 4hr film, for comparison:

MoS: 1500 vfx shots
BvS: 1500-1550 vfx shots

Moreover, ZSJL has more vfx shots than Avengers Endgame

Zack's team completed them all under a year with a rumored budget of 70 mil (also used for add photography *and marketing I beleive)

( #SnyderCut was announced May 20, 2020 and was completed anout a month ago)

Trailers usually don't contain finished shots and I believe the 2nd trailer was supposed to release soon after New Years like Zack said on one of the livestreams

So it would explain why 1 or 2 shots might look a little wonky

Another explanation is that 2800 shots is A LOT and some are bound to be poorer than the rest like the cyborg shot

Another rumor is that the trailer reworked the vfx to hide the knightmare cynorg suit, but then again, why even show it at all?

I'm not saying it's not a possibility, it just seems unnecessary, if the final shot in the film still looks like that then it is what it is I suppose

@khan250101