Decent build that needs only a couple of changes.
This build is EXTREMELY offensive so u will be targeted a lot in team fights I recommend taking flash or ghost for a getaway since Malzahar has no escape method.
Also try to take primary runes. Such as ap per level or cool down glyphs and health seals or mana per level seals, it has a greater effect than magic pen glyphs or ap per level seals.
It's also recommended taking null zone before lvl 6 so when u use your ulti on a guy over a null xone, you'll see significant damage increase.
Fix the masteries for offense u have a point for improved exhaust which you are not using and in utility u have improved clairvoyance which u don't have.
If you do take mejais u need an escape method like I can said or else it's pointless going for it, you'll be expecting more deaths than u want

Very good Build! The fact that I have enough life and mana but is a skill that does damage! Possessed 17 frags 4 deaths and 21 assists! Great Build! Thx Kojol de Besciak!