Zagara

level 1: i go with demolitionist because it just helps destroy the keeps quicker

level 4: envenomed spines is what every build usually gets

level 7: again i'm picking talents to help kill the keeps

level 10: self explanatory

level 13: this one doesn't really matter i just prefer bile drop for instant damage

level 16: Banelings are op so more of them helps

level 20: i like to use bolt of the storm just in case **** hits the fan i can teleport past the wall and escape

Abathur

level 1: helps the locusts which help u push lanes

level 4: need this or you can poop on the towers

level 7: most useful talent here

level 10: Cloning so you can help destroy the towers

level 13: helps locusts so it helps us

level 16: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

level 20: locusts op

im not really sure about abathur, i never really play him, but i would say that the only things you really need are the cloning (level 10) and ballistospores (level 4)