I've have been working on this deck for a long time now and I know it still has some major flaws but I just can't see where to improve them. I really have trouble on choosing a focus for the deck it could early be a mill deck/a combo and the Vulturous Zombie is aggro. Even if you don’t reply I want to thank you for all the deck you do post I always look to them for help first. Oh well here the deck list:
Land
1 Minamo, School at Water's edge
1 Torest
4 Overgrown Tomb
1 Shizo, Death's Storehouse
1 Okina Temple to the Grandfathers
4 Breeding Pool
1 Urborg
1 Urbog, tomb of Yawgmoth
6 Island
Creatures
2 Szadek, Lord of Secrets
4 Birds of Paradise
2 Vulturous Zombie
3 Wall of Tears
3 Shadowmage Infiltrator
1 Spirtmonger
Spells
4 Putrefy
2 Glimpse the Unthinkable
4 Hesitation
4 Memory Lapse
4 Temporal Spring
3 Exhaustion
2 Panoptic Mirror
Sideboard
2 Panoptic Mirror
4 Infest
4 Eradicate
3 Cranial Extraction
2 Voidslime
Any constructive advice is helpful hope you reply -- L
Ah, constructive advice I can do! Let me introduce myself, my name is Sean, or as I’m more frequently known, “Sean from NY.” Imagine my surprise and pleasure at being asked to work in the Deck Garage for Pojo. Well, I have no problem helping others improving their decks as best I can. Let’s look at what our friend L here has got for us… Ah, a deck that mills and uses Vulturous Zombie to make full use of the milled cards? Interesting, most interesting.
Firstly, unless my math is wrong, I believe this deck is 58 cards, and the minimum for magic is 60, so we’ll have to make sure that the deck has at least 60 cards at the end of this. Something I’d like to address is the presence of the Legendary Lands from Kamigawa. These lands were very useful in Kamigawa Block because a very high number of cards in the set were Legendary. However, aside from the other lands, only 2 cards in your deck are Legendary and as such you are not going to get much benefit from them, so we can take out Minamo, Shizo, and Okina. While it is very interesting to see Urborg and Urborg, Tomb of Yawgmoth in the same deck, neither is terribly relevant to the deck’s goals (now, if you had a lot of swampwalk creatures that’d be a different story) so they can come out as well. We’ll get back to mana base in a bit, but I’d like to move onto the meat of the deck; the creatures and spells.
Birds of Paradise gets a thumbs up because it provides acceleration and the more acceleration you have, the quicker your deck can develop. I almost let Wall of Tears slide, but there are many creatures with comes-in-to-play effects that you do not want to bounce, so take them out and add Minamo Scrollkeeper. It’s the same cost, can actually kill things that run into it, and it will let you hold more cards. While I favor the Scrollkeeper, you could also replace Wall of Tears with Drift of Phantasms. It flies, is a 0/5 for 2U, and can transmute to fetch things with a converted mana cost of 3. However, with a Transmute cost of 1UU it might be a bit of strain on your mana. 
Shadowmage Infiltrator is another good card; he pokes your opponent and draws you cards. As a matter of fact, you should if at all possible try to increase his count to 4. Vulturous Zombie will of course be staying, and since he is the big aggressive beater of the deck, I’d strongly recommend that you increase his count to 4 if possible.
We’ve looked at what’s good; now let’s take a look at what should go. Szadek, Lord of Secrets, while being one of my favorite vampires is unfortunately more flavorful than he is powerful. His flying, 5/5 power and toughness, and his ability are all very appealing, but his cost of 3UUBB is a major draw back. After all, you want to be able to summon your Vulturous Zombie and then begin to start attacking your opponent’s deck to make it bigger.
And then there’s Spiritmonger, the proverbial elephant in the room. Spiritmonger is a powerful card, but it’s not connected to the main idea of your deck and you only have 1 of it, and 1 of’s are reserved for cards that will win you games within a couple turns. So, out it goes.
Next let’s take a look at your spells. I first wondered why you had just 2 copies of Glimpse the Unthinkable (I understand they’re expensive) and I was going to take them out, until I saw Panoptic Mirror. Then I grinned widely as I realized just how nasty this deck could get. Now, if you can get 2 more Glimpse the Unthinkable then this deck can afford to become a great deal more defensive and focus purely on imprinting Glimpse onto the Mirror.
Putrefy is definitely good removal so it can stay, and as I said, I like Panoptic Mirror, in fact, I like it so much I think you should take 1 of them out of the sideboard and move it main deck.
Unfortunately this is where I really begin to eviscerate the deck. Memory Lapse is a good counter, but quite frankly, there are a lot of spells you don’t want your opponent to resolve, so for that I’d recommend Mana Leak. It’s the same cost and it tends to be a more permanent solution, particularly earlier in the game when you’re opponent will not have 3 mana to spare.
Hesitation is ok, but keep in mind you’re opponent will see it and be able to play around it. So if you can I’d recommend replacing them with Rune Snag from the Coldsnap expansion. It’s got a very Force Spike flavor to it that just gets better as you use them.
Temporal Spring is a nice card and it’s definitely annoying, but I feel that you’d be better off taking it out for Last Gasp. At 1B it’s cheaper, easier to cast, and almost always a more permanent answer.
As for Exhaustion, you can do better. Replace it with Golgari Signet, you’ll benefit from the mana acceleration it can provide as well as making your Putrefy and Vulturous Zombie easier to play
Ok, now that we’ve addressed the bulk of your deck, we can return to the mana base and make a few more tweaks. Overgrown Tomb and Breeding Pool are both very good, but I’m curious as to if Watery Grave would be a better choice, but since it’s rather expensive, don’t sweat it. To make casting out the Infiltrator easier I’ve added 3 Dimir Aqueduct to your lands, decreased the Island count to 5, increased the Forest count to 2, and added 3 swamps. I’m no expert in mana bases so by all means, experiment with it. Nothing I change here is cannon; the best experience you can get is by playing around with it until you find something that’s comfortable for you. And of course, no deck can expect to win always. So, at last, I present to you, L:
Deck and Decay v2
15 Creatures:
4 Birds of Paradise G
3 Minamo Scrollkeeper 1U
4 Shadowmage Infiltrator 1UB
4 Vulturous Zombie 3BG
24 Spells:
2 Glimpse the Unthinkable UB
4 Mana Leak 1U
4 Rune Snag 1U
4 Last Gasp 1B
4 Putrefy 1GB
3 Golgari Signet 2
3 Panoptic Mirror 5
21 Land:
4 Overgrown Tomb
4 Breeding Pool
3 Dimir Aqueduct
5 Island
3 Swamp
2 Forest
15 Sideboard:
1 Island
1 Golgari Signet
1 Panoptic Mirror
4 Drift of Phantasms
4 Infest
4 Cranial Extraction
I’m no expert in sideboards so this is my humble opinion on what might be useful for you. Eradicate is just a bit too situational for my taste, and it belies a very heavy commitment to black. If you can get another copy of Cranial Extraction you should, it can positively neuter combo decks. Infest is ok, particularly if you’re dealing with a swarming strategy, and I’ve added 1 Island and 1 Golgari Signet. As for the 4 Drift of Phantasms, well, I liked them, but I liked Minamo Scrollkeeper more. Play around with it and find what works. I wish you the best of luck and may your Vulturous Zombie’s always swing for at least 13!
