Member Rara Avis
All pronouns come in three flavors: subjective, possessive, and objective. For example, we have he, his, and him respectively. And, yea, we also have who, whose, and whom. When in doubt about which to use, just substitute all of your who flavors for the appropriate he flavors, and let your ear decide.
"From he to he?" Nope, doesn't sound right.
"From he to him?" Still doesn't sound right.
"From him to him?" Okay, that sounds pretty decent.
Ergo, the correct form would be "From whom to whom?"