>>19233
Not really. They're big dogs, but their asshole isn't automatically "2x normal dog" size. Their shits are not larger in diameter than any other big dog, the volume may be more but the plumbing is still pretty much the same size as a mastiff or rottie.
I don't know why you would want to do such a thing anyway other than to see if it could be done. Geometrically, very difficult to achieve, maybe one below and one above, but hardly practical and certainly not comfortable for anyone, including the dog.
Dogs don't generally enjoy anal though some will tolerate it. There are some exceptions but it's rare. Stretching to fit two cocks may be possible but I doubt it would be enjoyable for the dog.
Just bc you've fantasized about this scenario doesn't mean it's happened, and released on video as well.
Closest I've seen was a dp of an Akita bitch, one doing anal and the other in vagina.