I have another idea,

The puzzle creator said the only thing all the private keys have in common, is that all of them were created from a HD wallet, and then masked from the left with zeros.

Is it any weakness on the HD method of creating wallets? I mean, with the number of private keys already revealed, we could just try to target the searches for the the master private key that was used in the HD wallet.

What do you think?

Regards.