If Zira never fell off the edge...

[DGFone]

She would have left in search of some other lion/pride to help her not only defeat Simba, but Kovu, Vitani, and every single other traitor to her cause. Basically, if she survived, the Outsider's betrayal to Simba's side would have meant that however little sanity Zira had left would have been decimated.

[Meskhenet]

If Zira never fell off the edge then I think the ending would be a complete twist of the movie and it kind of goes the whole Romeo and Juliet theme of The Lion King II: Simba's pride movie.

[Kipekee]

I think there'd be like a flood where she went as a loner, and she'd drown like the cliff.