If they are still napping, as someone else suggested, it may be time to give that up so they can sleep at night.
I don't understand how they are both in poopy diapers for so long that they are smearing it all over the room. I know twins do a lot together, but synchronized bowel movements is pretty amazing. I'd feed them much earlier in the day so that the poop works its way out long before bedtime. There needs to be a bedtime routine that is calming and without deviation. Bath time (ideally after that last poop!), teeth brushing, then into the room for story and lullaby and good night cuddling and kisses. No talking, no playing. If they fool around, there's no story.
I'd take away the toys that are getting covered in poop and tell them that they can't have them back until the poop stays in the diaper or in the toilet. No other options. No touching poop - it has germs and makes you sick. Removing the toys will give them a lot less to do in that room.
I would also consider separating them even if that means putting the 1 year old in your room, or putting one of them in there with the younger one unless that's going to be a bigger disaster - although at this point, it's hard to imagine a bigger disaster! Each parent takes one twin and is responsible for getting that child to be with a special time - each child picks a book and has quiet, alone time with one parent. The next night, the parents switch but the routine is the same. The child doesn't pick the routine, just the story and maybe a quiet CD with appropriate lullaby music. No choices about whether to get up and do something different, and if they act up, they lose the story and cuddle time.
There's got to be a way to secure their clothing so they can't get everything undone. But quiet time and insistence is more important. It's possible that you and your husband are just worn out from the day's activities and getting the 1 year old settled that you have less patience at 8 PM. They may pick up on your agitation and do everything possible to increase it. They're getting lots of attention and a reaction by spreading poop everywhere.
I'd consider putting the 1 year old down and immediately going into bedtime for the twins - they may be seeing the evening as "their" time after the "baby" goes to bed, but night time needs to be quiet time with all the playing done during the day.