Fox: You can simply add in a frame speed modifier event in the ending Animation. Or, you can alter the animation in BrawlBox, but then you would have to change timers in PSA to match the animation. The blaster damage however would need Brawlox to edit. Get yourself BrawlBox v0.68b, open the moveset data, find the articles folder, open Article 1 which is his Blaster Shot, find the SubAction that has Offensive Collisions, and alter the parameters of that event.
Pit: Sadly the up specials for both characters rely on Article Floating Points (which can also be altered in BrawlBox), so can't help you out here.
Zelda: Like fox, use a frame speed modifier event, or change the animation.
I do have a
Tutorial for Special Attacks if that helps...