The text of the Corwin amendment:
No amendment shall be made to the Constitution which will authorize or give to Congress the power to abolish or interfere, within any State, with the domestic institutions thereof, including that of persons held to labor or service by the laws of said State.
The thirteenth and fourteenth amendments were passed prior to the proposed ratification, so this would have no effect except to block the Kanye West proposal of repealing that portion of the thirteenth amendment that allows involuntary servitude as a punishment for a "duly convicted" crime.
The "plain text" of the amendment does not legalize slavery. It simply says that the constitution can't be amended in the future to make slavery illegal. Since it is not necessary to amend the constitution in the future to make slavery illegal, the plain text of the Corwin amendment would have negligible effect. It certainly doesn't repeal any amendments.
It is possible that there are some other amendments that might be blocked by this one, but of course this amendment would itself be subject to repeal. It does not use the same kind of language as the equal representation in the Senate clause. And it's questionable if it did if it would be enforceable, as that would create a situation where an amendment was easier to pass than to repeal.