Umberto Cassuto was a Jewish scholar who gave a series of lectures in the 1940s-1950s in Rome on the different references to El/Elohim vs. Yahweh in the Pentateuch. His lectures were published in 2006 as a book entitled "The Documentary Hypothesis and the Composition of the Pentateuch".
In his lectures, Cassuto convincingly shows that the use of both El/Elohim and Yahweh shows, not multiple authors, but rather different theological perspectives. Moses used El/Elohim when referring to God in his universal role (such as Creator or Judge, or when dealing with all creation and all nations) and Yahweh when referring to God in his personal, covenantal role with Israel.
I've always been highly skeptical of source criticism (the basis for concluding that there were multiple major authors of the Pentateuch and that it was not compiled until 1000+ years after Moses) for at least the following reasons:
- Source criticism is not subject to falsification
- Source criticism conclusions cannot be confirmed or verified
- Source criticism is highly subjective as demonstrated by the fact that no two "experts" in it can agree as to their conclusions
- Proponents of source criticism ignore all evidence that contradicts their theories and conclusions (e.g., there is much in the Pentateuch that supports a single, very ancient author)
- Source criticism actually began with other ancient classics and has been largely abandoned in that field
- The main motive behind source criticism appears to be, not a search for truth, but an attack on the credibility and reliability of the Pentateuch.