A faster and more efficient way of moving your photos to another account is by sharing a link to the photos between the two accounts.

1. Log in to Google Photos using the account from which the photos have to be transferred.
2. Select the photos you want to transfer as explained above. Alternatively, move them to a new album and share that album with your second account.
3. To create an album, click the '+' sign on the top right after selecting the photos you want to share.
4. From the options that appear, select 'Album' to move the photos to an album.
5. You can move the photos to a new album or an existing one. For transferring photos to your second account, click the 'New Album' option.
6. On the next page, you can add a name to your album, such as 'Shared'.
7. Once the album is created, click the share icon on the upper right side to view the sharing options.
8. Google Photos will suggest a few contacts with whom you can share the album.
9. At the bottom, you will find a 'Create Link' option. Click on it to create a shareable link.
10. Google Photos will notify you that people with whom the link will be shared will have access to the album. Click the 'Create Link' button to continue.
11. Once the link is created, copy it manually or click the 'Copy' button to share it.
12. Now, sign out of this account and log in to your second account, or log in using a different browser.
13. Paste the link you copied into the address bar, and you will get access to view the album.
14. Click the 'View Album' button to view the photos in the album.
15. Now, select the photos you want to transfer to this account and click the '+' sign to create an album here.
16. Finally, create a new album and name it something like 'Transferred' as you did with the other account. The photos will be added to the album in this account.

Note: Make sure the upload quality for your second Google account is set to 'Original' so photos are uploaded in high quality.

In the same manner, you can select and move all your photos from one account to another. ///

Google Photos is smart enough not to duplicate pictures. So transfer albums like this, then start selecting ALL the pictures in the old account. In the new account, create/add them to the same album ("!Old account" for example). These will show up in your new account.

Once they are all transferred, you can delete the "!Old Account" album; the pictures will remain.