First of all let me say that this is my personal build maybe you find him not good but this is how I prefer to play MALZAHAR depens on your playstyle. this is also a very simple and fast guide

Lets start with the runes
for the runes i have aggresive AP runes.

-8.55 Magic Penetration (Marks) (greater mark of insight)
-3.69 mana regen/5 sec. (Seals) (greater seal of replenishment)
-10.8 abilty power (Glyphs) (greater glyph of potency)
-14.85 abilty power (Quintessence) (greater quintessence of potency)

i prefer to take this runes because MALZAHAR is a mid to late game champion thats the reason why i take this runes for that early game boost and the mana regen for standing longer i lane

WARNING: this rune page depens on your playstyle

About the masteries i dont have much to say
21/0/9 are very standard AP Mid runes
And this masteries can you use for almost every AP MID

as I have already said, MALZAHAR is a mid to late game champion
so he is a bit week before level 6 but after that he is very strong champion
MALZAHAR got a very deadly combine
it goes like this: drop you Null Zone (w) be sure you drop it on the place where the enemy stand and directly after droping your Null Zone, Ult Him when he stand in Your Null Zone for double damage. your Null zone dealing damage in % so it dont really care of Your enemy gots many health or just very low health also if you ult and Your null zone are not enough Drop you Q and your E on your enemy for the kill

Tip: Before you Recall drop your E on a minion thats give you the opportunity to farm as well as you are in base because every time you E kill a target he will was on a another enemy target

I hope that you liked my guide/build
i want to say sorry for my bad english but english is not my native languages
please leave a comment with what I did well and what i could do beter
this was my first guide

thanks for reading and using my guide