Sign in to the source Google account
Open Google Photos
Select the photos and videos you want to move
Click Share
Create or choose a shared album
Add the destination Google account to the shared album
Sign in to the destination Google account
Open the shared album in Google Photos
Select all photos and videos in the shared album
Click Add to library
Verify the photos and videos appear in the destination account library
Repeat for any remaining photos, videos, or albums
Download the photos from the source account if you want a local backup
Upload the downloaded files to the destination Google Photos account if needed