Can multi-encrypted file be decrypted with one password only?
Theoretically speaking, there is a possibility that a specific hashing algorithm can hash two separate passwords that both result to the same hash, however the odds of such an event making much of a difference in a brute force attempt is minimal. In addition, if there are two separate file containers (one inside the other), a brute force attempt would stop after decryption the outside container. My recommendation for encryption would be AES-256 encryption with SHA-512 hashing as those are currently accepted as industry leading algorithms. Should you care to, veracrypt will give you an option nest encryptions such as Serpent-Twofish-AES which will in turn make decryption take more time.