delete apple account, then transfer other apple account to same email

Apple probably has very good reasons for not allowing account merging. I presume its objective in designing things is not to make their customers miserable. I can think of several reasons for not allowing merging but since we are not supposed to speculate here I won't. Perhaps you can do the transferring of address as outlined above. If not, the things below will help you in doing ongoing or one-time transfer of as much as possible from one account to the other, but some things can never be transferred (namely purchases), only shared. If you need/want to share then you will have to not delete the old account.

You can use various iCloud sharing features for some ongoing data sharing.

Share folders with iCloud Drive --> Share files and folders in iCloud Drive on iCloud.com - Apple Support

Read How to use Shared Albums in Photos on your iPhone, iPad, and Mac - Apple Support about how to share photos.

Sharing music playlists —> How to share an Apple Music playlist on your iPhone or iPad - Apple Support

Apps and media bought with one Apple account are permanently associated with that account. Look into using Family Sharing to continue to be able to use items purchased with one Apple account with other Apple accounts, and for some data sharing features.

- Family Sharing - What is Family Sharing? - Apple Support

- Set up Family Sharing - Set up Family Sharing - Apple Support

The next section may sound tricky but it lets you merge some things on a device where you have already signed in with an old account but want to use a new account and incorporate data that is already on the device from the old account. Incidentally, the data will then propagate to other devices using iCloud with that new account. (I haven't tried this with a computer but it may also work with a computer account signed into an old account.)

If you have signed into the first Apple account on a device then fortunately when you sign out of that account it asks you if you wish to retain the data from the old account on your device (toggle the ones you want to on). If you keep data on the device then when you sign in with the other account it will merge this data with the account signing into the device. You can later delete individual items from the old account that you do not want. Similar information can be found in this post: I have 2 apple IDs i want to merge them h… - Apple Community , and a step-by-step in this User Tip: How to “unshare” an Apple ID - Apple Community . Note that only content physically present on the device such as contacts, photos and videos will be retained. Meta data such as a game play scores that are tied to a specific account or are only on a vendor's Apple Account-specific database remotely will not be retained. Also turn off storage optimization before doing this. With Optimize Storage, smaller, space-saving photos and videos are kept on your device while all of your original, full-resolution versions are stored in iCloud. Make sure photo optimization is turned off so the full quality versions from the old account are actually on the device before merging the content into your new account. Manage your photo and video storage - Apple Support You can turn optimization back on again once you are fully using your new account on the device.

Even though apps may remain on a device and may work for a while, you will not be able to update them or redownload them unless you buy them again with this account or download them with this account using Family Sharing.

Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac --> Sign out of iCloud on your devices - Apple Support

If this involves a device changing ownership, the person should also change the ID set in Find My. Turn off Find My on your devices and items - Apple Support

If another Apple account is signed in you may need to enter the password for that account to sign out of that account first.

Click on this link to learn how to 'Sign in with your Apple ID' --> Sign in to your Apple Account - Apple Support

It is not supported to merge apple accounts, but it is also not supported to use an old apple account as mail address for another apple account. You can request the deletion of the old apple account, but then it is not possible to use it as mail for your current apple account I am afraid. What I should do if I where you is to make a new mail address and use that as your current apple id

From my understanding of what you want I can offer more optimistic information. The "no merging" thing—while true in a basic sense (an often unfortunately presented as the sole, definitive answer)—is not the entire story.

You can remove an address for an account while replacing it with another, wait 30 days, then use the on-hold address as the email address for another account. This is a very recent change by Apple and I think not all the contributors to this forum are aware of it. They key thing is to not delete the old account until your 30 day wait is up. If you delete the account, the address gets put on hold for 6 years. So you may need a spare, throw-away email address for holding the old account until the address is safe to use with the other account.

Change your Apple Account primary email address - Apple Support

- If you remove an email address from your Apple Account, it can’t be associated with another Apple Account for 30 days for security reasons. <-- NEW!

If you can’t change your Apple Account primary email address

- If you try to change your Apple Account to an @icloud.com email address that was created within the last 30 days, you will be asked to try again later.

- If you see a message that the email address you want to use isn’t available or is already in use, check that you or a family member aren’t already using that email address with a different Apple Account. If a family member is using that email address, remove it from their account, then try to use it.

From: How to delete your Apple Account - Apple Support

“Can I use the primary email address for my deleted Apple Account to create a new Apple Account or with another existing Apple Account?

No, once your Apple Account is deleted, you can’t use the email address that you used with it to create a new Apple Account for as long as Apple retains the one-way hash of the email address. For third-party (non-Apple) domain accounts, the one-way hash is deleted after six years. For other accounts, this is retained according to Apple's retention policy, which is reviewed regularly. In addition, you can’t use that email address with another existing Apple Account except as a rescue email. Also, if your primary Apple Account email address is with a Custom Email Domain, it can never be reused to create an Apple Account after your Apple Account is deleted, even if the domain ownership changes.”

Because of the complexity of your situation my post will be too long for a single post, so read the next one by me too...