Apple Id - Way to sync two ids?

I hope you can bear with me on this query and that I can make myself understood, I did send apple support a query, but they did not seem clear on what I was asking. I have also googled my query under a variety of questions and it would seem that what I want to do is not possible, but I said I would ask here before creating new ids and editing email addresses.

Many many moons ago I had an ipod and registered it under my eircom.net email. It broke and I didn't replace it until recently. In the meantime, I got an iphone, that I registered under the same email address. I stopped using the eircom.net address, due to spam and I didn't find it very user friendly. I got a gmail.com address which I have been using since. Some time ago I seem to remember trying to log in to the eircom.net address to find something and got a message telling me it was no longer valid.

I recently got an ipod nano and registered it using my gmail.com address.

My problem is this, I cannot purchase apps on the iphone or use icloud as it wants me to verify my email address. I can't verify it as it is the now defunct eircom.net address. I thought I could edit the old email address to my new one but as it is already registered to my ipod nano, it is telling me that this is an existing apple id.

Is there any way I can change the apple id of the old email address to the new email address without having to create a new email address.

Hope this makes sense.

Thanks in advance.

What you need to do is in iTunes, unregister your iPhone from the eircom address (de-authorise it) and re-register it to the new gmail address.

If you have made purchases on iTunes or the App Store on the old iPod or the iPhone using the old eircom address these will probably not be available to you.

I hope I have interpreted your post correctly and AFAIK you cannot have a device registered in iTunes, iBooks, App Store with different email addresses due to digital rights management (DRM) controls as administered by Apple