Righto.
Here we go.
First flashback (hospital - 2006)
Zoe says to the nurse "There's only one, where's the other one?"
< KEY POINT >
Nurse looks shifty and replies "Dr will come in and speak to you when you're feeling better..."
Zoe mutters "bad blood bad start" and then says she "I want him adopted".
Nurse goes off to speak to Dr and then they both go back to Zoe to find she's scarpered and left the Ibiza key ring behind.
So, not one of the medical professionals said anything definitive about the other baby.
Next flashback.
Zoe in bar with Max says she hasn't got any kids.
Then later in bed, he says "so you've got a kid"
Zoe replies "2, one died the day she was born. The boy, he survived".
So, it was only Zoe who said anything about a baby dying.
No Nurse or doctor confirmed either way.
From this extensive research, and let's be honest - this being EE - 100% means both babies survived, and will be wending their way to E20 via a black cab on a screen near you, very soon!