I am so sorry that you are faced with this decision, it is not one I would wish on my worst enemy. I have made the choice twice, once with my beloved Bandit, because his arthritic hips were so bad that he could no longer function, and nothing the vet could give me was controlling his pain. The pain was so bad that his sweet and loving disposition was changing, and I could no longer trust him with my children. To make matters worse, he was my son's best friend and companion for 12 years. We went together to the vet, and stayed until Bannie was gone, and I will never forget holding my 16 year old as he sobbed out his grief and his heart broke.
The second time was Rocky, a 10 month old doberman puppy. He ran in the door and dropped dead at my feet at 8 months old. Dale performed CPR and got him breathing again, and we rushed him to the vet. They were unable to give me any diagnosis at the time, and we began a nightmare of vet's visits with barrages of fruitless diagnostic tests as his health declined and he stopped eating, and lost wieght. He came home from his third stay at the vet's office, this time with a diagnosis of pnuemonia, and was dragging himself to the door to greet me when I came home from work, and I looked at him...really looked at him. His stub of a tail wagging 250, his mouth open in a doggy smile as he staggered his skelital self across the kitchen to love on me. He looked at me with that look, and I knew it was time.That evening we sent him to the bridge, and some measure of peace. Years later our vet was finally able to give us a definitive diagnosis of coppertoxicosi s,a genetic disorder that was relatively unknown and incurable at the time. Sadly, despite being notified of this disorder within her lines, and the availability of testing for her breeding stock, the breeder denies it's presence in her dogs and continues to breed, prducing carriers and affected dogs.
Although I feel for your famly and Zoey, I think sometimes you just have no choice left, and you do the last thing that you can to care for your beloved baby. You let them go.
Stella