So Snapchat has made it more-less impossible to remove memories.
I had around 10,000 memories and most of those were videos of old memories over the years.
Every time I tried to export more than 30 photos/videos it would crash my phone (iPhone 11 pro max) so no issues with slow hardware.
I did a lot of research online and couldn't find any solutions so I started trying to figure out how I could solve this issue.
What I found is if you go to https://accounts.snapchat.com/accounts/downloadmydata and request your data, mine took around about 30 minutes to arrive. Once you have downloaded the zip you open the "index.html" then go to the "Memories Tab" on that page you can see all of the information with the download button.
Snapchat decided that they shouldn't add a queue to this to download them all at once.
The code is really simple but very effective.
There is also an issue when using Chrome as when trying to download multiple files it asks for confirmation each time (Still an issue, try a different browser)
There also seems to be an issue with some EXIF data being pruned from certain files on a seemingly arbitrary basis.
So my workaround for that was I just used Safari because it doesn't cause problems, you can access the console by Option + Command + "C" then just paste the code inside.
As of 2021, Chrome still seems unable to download multiple files. This works perfectly fine on Opera/Safari/Firefox
In Firefox, you must go to settings, applications and then save file, otherwise it will just open the file each time its downloaded, Also type "about:config" and find "media.play-stand-alone" to FALSE
If you have any questions please feel free to comment, and I will try and help you out.