If multiple players on a server zombify and cure a villager, the most recent player to cure it will overwrite the other players' curing.
Steps to Reproduce:
1. Player 1 cures a zombie villager. This will result in Player 1 having reduced trade prices. Player 2 will have normal trade prices.
2. A zombie kills the villager, converting it into a zombie villager.
3. Player 2 cures the villager.

Player 1 will no longer have reduced trade prices, and player 2 will instead have reduced trade prices. This occurs even if Player 1 had cured the villager multiple times in a row. The single cure from Player 2 will overwrite all cures from Player 1.