Hi - zoladex will have the same effect on adeno as it is endo within the uterus. So what they are saying is that if the zoladex stops your pain it will have stopped the activity of any adeno, therefore you have adeno. But it really isn't as straightforward as that. Endo can feed itself by producing its own oestrogen that is not affected by zoladex and it is likely you probably have had endo left in from a lap in general gynaecology. Have you had an MRI because this will give an indication of whether adeno is present (it can't be conclusively diagnosed but a skilled radiologist who is used to looking for it and uses the right contrasts and weightings will have a good idea). This will also see if you have any deep endo that has been missed. I would say that should really have been the starting point.
The flare effect really should have ended now (usually around 10 days) so if you are having severe pain now it could be from endo producing its own oestrogen or from adhesions or nerve pain, none of which will be helped by zoladex. Certainly the only point of taking these medications is to help with pain not to aggravate it.
I think you should probably speak with the endo centre about it as I don't think it's normal.