This is my proposed breakdown for Kirby's Return to Dream Land. I guess it's pretty easy to identify each composer, because they have very distinctive styles; Hirokazu Ando usually goes for a "digital orchestra" similar to that of the Smash Bros. games, while Jun Ishikawa relies more on traditional instruments similar to those of the SNES Kirby Super Star / Dream Land 3.
The numbers on each track refer to the order in which they appear in the game's sound test. I also indicate the equivalent tracks on the official soundtrack (
http://vgmdb.net/album/33773)
Also, starred (*) tracks have been reprised on Kirby: Triple Deluxe, and therefore they are officially confirmed by that game's sound test.
UPDATE: Apparently Jun Ishikawa made Vs. Magolor and Hirokazu Ando made C-R-O-W-N-E-D according to a post on the Japanese Kirby Triple Deluxe Miiverse together with RtDL's liner notes (info taken from
here btw)
UPDATE 2: New songs confirmed on Planet Robobot (**). It seems like I originally got Landia wrong
UPDATE 3 (2018/19/01): Probably the last time I'll tweak this list, but I've retagged the tracks again coming from the formatting of the sound files. Aside from a few mistakes I guess it was pretty accurate.
JI - Jun Ishikawa; HA - Hirokazu Ando