I am NO where near an expert in this area. But we have just gone through this---or are going through it.
But the introduction to Jasper to his new home & our current animals went MUCH better then I ever expected.
I think it depends on Zeus's tempermant & how you feel he is around other dogs. Our older dobe Copper (now over 13)
is pretty laid back. Our biggest issue was we didn't want him to feel left out. And we also did want the puppy
to be too hard on him--since he has trouble with his hips these days.
On the first day home. We brought the puppy out in the front yard first... Then brought copper out to meet him (on sort of
non territorial grounds first) The puppy was VERY interested in him--but Copper sniffed Jasper once & went on to go
the bathroom. Jasper came from a home with 3 other adult female dobes--which I think was good--he was use to other big dogs.
At first copper didn't tolerate Jasper--just wanted to be away from him--because he never knew where he was going to jump or bite. We
would make sure they both had their own spaces & the other wasn't allowed in that area. Also made sure that Copper had tons of attention & never felt left out because of the puppy.
Within a few days, they were laying with each other and playing together. Jasper loves to lay with our 17yr. cat as well.
I think they were a comfort to him, after being away from his litter mates.
Good luck to you--i'm sure it will go very well!