[Lupin]

If they are just livebearers, I wouldn't bother with saving them. If you provide them thickets of plants, then the strongest will obviously survive.
Livebearer fry aren't known good hiders for nothing.

They are quite prolific. Let alone the findings that one single mating from a male will allow the female to produce several batches of fry in months.

Take note, never use breeder nets or breeder traps. They can cause more harm than help by stressing the fish as they have nowhere to hide or take refuge.

 

[Lupin]

Zebra danios don't get pregnant. Pregnant is a term used for mammals.
Fish using internal fertilization like the livebearers are referred to as "gravid".
Fish using external fertilization are referred to as "ripe with eggs".
Danios are egg scatterers.

If you can buy another tank, place two layers of marbles as substrate and make sure water is at half level. Then place a shoal of danios inside the tank. 6 is preferred. Males are generally slimmer. Females are plump and almost full of eggs.
With water at half level, the eggs fall faster and slip between the marbles thus predation from adults is averted.
Adults will quickly eat the eggs as soon as they scatter them hence my advice for half-level of water.

Remove the adults after they are done with spawning. Then add Methylene Blue in the tank to protect the eggs from fungus. Aerate the water.
Prepare some brine shrimps or buy liquifry which is available in the lfs.

If not, prepare a hard-boiled egg, then scoop the egg yolk and suspend it in the water in a jar.
*Use this method only when fry is free-swimming.

The fry when hatched have yolk sacs and will stick to the area where they have hatched. They will be free-swimming after a few days in which time they'll search for food.
Provide some riccia fluitans(plants). they harbor microorganisms which serves as food for the fry.

 

[Lupin]

Livebearer fry will readily eat anything so anything you give is ok. If you have granules, soften them and keep squishing them to produce small particles which the fry will readily eat. I do that on my discus as they are quite slow in munching the food.