Zotero used to be able to import the Mandeley's database. However, Mendeley 1.19 encrypted my data on my HDD with a key that only Elsevier has. See here:
Mendeley 1.19 and later have begun encrypting the local database, making it unreadable by Zotero and other standard database tools. Elsevier made this change a few months after Zotero publicly announced work on an importer, despite having long touted the openness of its database format as a guarantee against lock-in and explaining in its documentation that the database could be accessed using standard tools.
Mendeley claims that they were compelled to do so by GDPR:
We have encrypted users’ databases to comply with GDPR. You can still export your libraries to get data locally and/or import into another reference manager.
They also claim that I can export my data, but this is not true. Mendeley would only export basically a list of DOIs, and I am losing all the organization in folders it took me months to make.
I have zillions of articles: I can't afford to have them all in one folder in Zotero.
People are trying to break the encryption but I am not able to do that.
Can I ask them to provide me with a copy of the unencrypted database under art. 20.1 of GDPR?
Can I ask them to send the data directly to Zotero under article 20.2 of GDPR?