Q: If Double Agenda is on the table, and each Goal requires a different Creeper can you win by fulfilling both Goals?

For example, if the Goals were He Bravely Ran Away (requires the 3-Headed Giant) and Rabbits of DOOM (requires the Killer Rabbit).

A: No, not if they are two different Creepers like this. The 3-Headed Giant you need to win with He Bravely Ran Away prevents you from winning with Rabbits of DOOM, while the Killer Rabbit you need for that prevents you from winning with He Bravely Ran Away.