I've read that Hans Zimmer is somewhat unusual in the music industry in how readily he will co-credit his work with others. He explained that while he might compose the melody, he will often use vocals like in the Lion King Soundtrack, that without the input of another artist, his tune will lack the core spirit.
This is why for most of the Lion King soundtrack, you will see "Hans Zimmer and Lebo M", and for many other songs that he composed, but another person sang in, he will readily give them co-credit. Another famous example is "Now We Are Free" from Gladiator.
Thumbs up to this man!