EARLY:
Try to cast down Necromancer's Stockpile, Endless Ranks of the Dead, and a lot of zombies. Cast a few Duress to make opponent(s) discard some cards to make the field safe.
MID:
Cast more zombies, and by now, should have a great horde of zombies because of Endless Ranks of the Dead.
END:
Cast the last bit of zombies and keep making the horde grow bigger by discarding cards for Necromancer's Stockpile, Skirk Ridge Exhumer, and Zombie Infestation to get a truly big horde and attack with all to deal some really heavy damage. If opponents some how destroy all the zombies cast down Zombie Apocalypse, retrieve all the dead and kill all humans.
THE END:
Play Whip of Erebos and/or Bow of Nylea to make zombies have deathtouch and kill huge creatures when they attack. They also get lifelink to gain a lot of life from all the zombies in the horde.
COMBOS:
Waste Not combo with Persecute. Amazing creatures, anything makes you stronger when you Waste Not!

NOTES:
More zombies joining the deck soon.
Play safe against blue or/and white decks.
Not good against decks with flying creatures.
Working on this deck for maximum zombie synergy.
Play testing with deck on Untap.in