Duplicate photos not detected - MacOS / IOS

I've recently moved all my photos to iCloud as well as creating a Shared library with another iCloud user. The whole process saw an increase from around 60K photos on my Mac to 90K photos in the iCloud library. This is due to a huge amount of duplicates appearing. Unfortunately these aren't being detected as duplicates as the file formats are different (HEIC & JPG). I spoke to Apple support and they said there is nothing I can do other than remove them manually. This of course is a huge manual task and most probably not achievable.

I wondered if anyone knew of a way to get around this - i.e. identify and/or remove the duplicates despite the differing file format.