Hi, i love the necromancer with zombies, so i just have to answer
Attack Spells
Normally as a zombie necromancer you should never have to use the Chain Lightning or the Ring of Fire.
Ring of Fire has the disadvantage, that it hits your zombies too, when they are protecting you. Chain Lightning is a good strategie to ensure that the enemies are vulnerable to bloodthirst. But there are better ways: Idol of pestilence comes into my mind, so you can spend the spellpoints for these attack spells in a better way. (Acid Ball!!)
Conjurations
Graveyard is most effective, when creatures are destroyed and it receives their level as mana. But what if you are fighting a one-man-army without creatures ... and he goes straight for your mage? The graveyard is in that case less effective. I prefer the Libro, because its cheaper and gives me the ability to spawn where i am.
Creatures
Your Zombies are a good start. You should consider to put in more non-pest-zombies, so you can be guarded by multiple undead instead of only 1 brute.
Enchantments
As a dark mage, in my opinion, you lack diversity here. In this category there are very effective ways to deal with flyers or to protect your zombie army. Agony is a great curse that's very handy in every game. Chains of Agony, Rust, Debilitate (Valshalla, Gorilla etc.) should be considered too, so you can adjust your playstyle to the enemy. I also like Plagued on one of my zombie brutes
Equipment
When protected by your zombie army, you should not be attacked, because you are guarded or because your zombies spread fear. there is no need to go for a mana costly armor. Dragonscale Hauberk could be the better choice here, especially because there are now 3 mages out there using fire.
What conditions do you want to remove from your mage with the Healing wand? you are immun to poison, your zombies are too. Acid is not that scary, when protected by your army and cloak of shadows. I would take a second Armor and Cloak. last thing ... dont waste 5 mana on mage wands. 3 zombie frenzies are more than enough to win a game.
Incantations
Explode is a very costly spell. What you want to do is: Pumping out the zombies and frenzy them to the enemy. There is no room for a big mana investment to explode enemy items. that brings you to the point, where you are canceling your second action because you need all the mana for 1 explode. dissolve or acid ball work better.
Repulse is in your matchup not a good solution. it hits your zombies as well and you want your zombies to stay close. and there is more ... you cannot control the direction of the repulse, so the enemy creatures could be thrown away from your hungry undead and thats not what you want. force push is a good thing and will be even better when using a wall of thorns, firewall or wall of poison gas. that way, you can separate the enemy mage from his army.
what i miss in your book:
nullify to protect you from being teleported out of your zombie army
more brutes to guard you and the graveyard
shagoth zora, even if its not eating, its a very cheap zombie
deathlock as alternative to poisoned blood
acid ball to weaken enemies armor
hurl bolder to finish off enemy mages
I hope my view can be a help for you
