My23 mnth old shih tzu keeps ppooing an weeing in the house she is or was house trained but now she's eating the poo she's let out last thing round 3am an were back up round 7 she's never left alone in the house for more than 2 hrs

I had a Jack Russell that used to do that. Its pretty normal for dogs really. I would try to discourage it though!

Try to clean up your dogs mess as soon as you can

Thanks amberpock we don't see her doing it she doing it in the time she is left when we go to bed at 3-4AM last time she's let out were up again at 7AM she only left 3 hrs at least while were in bed we see poo smears on the floor ? Tried vinegar but that's not worked

If she has 'forgotten" her training the first step would be to have her checked out by the vet to rule out any medical issues such as urinary tract infections or parasites.
If she gets the all clear then you can concentrate on the behavior.
You will need to start from scratch with the training,
Is she crate trained?
When and how much do you feed?
When is she walked?
As far as eating the stools, you will need to be very diligent in keeping things cleaned up.
It is not completely understood why they do this, there are many theories.
You can purchase products that will deter the behavior at your vets office or pet supply store.