This deck looks like shits and retardness
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It's all because of Black and Blacker Lotuses. If you use some other cards like Dark Ritual or Bubbling Muck, that would be fine too. Actually I think that control side of deck going to slow down the zombies.
How about use Jace Beleren for supporting Undead Alchemist?
Your building looks a little slow to me. Here's my Zombie Swarm build, it may give you some hints: http://www.mtgvault.com/ViewDeck.aspx?DeckID=243949
Rooftop Storm looks very useful. Btw, I printed the deck and gave it a test drive and didn't had any mana issues in 5/6 matches.
Use Counterspell instead of Cancel
Deck is great but gives over-needed mana. Need to change 2 to 4 mountains with some useful cards like Dragon Roost.