I'm still a pretty new player, but I've played a lot of Malzahar. I too have been looking at different builds, but the current meta build seems to be the best for the most part.
Like most champs, I would say the build order is pretty situational on Malzahar. That being said, I think ROA start is usually ideal. I try to go blasting wand first of I'm not having mana problems, since it gives you more lane pressure.
I've been been Faker recently and running scaling CDR glyphs and CDR boots, since Malz does great with CDR. This plus masteries will put you at 35% at lvl 18, which should be enough. I prefer getting CDR boots since we won't be building other CDR items, and we'll have enough mpen from the rest of our build.
If you're not running sorc boots, you might need an earlier void staff. Just depends on how much MR the enemy team builds. You could build a haunting guise for a flat mpen boost. If you're really fed or they have no MR, you can always rush a deathcap.
So in most games you'll want your first 4 items to be ROA, boots, void staff, and Rabbadons. The build order is situational on enemy team comp.
Liandrys is mostly a late game item. Malzahars AP ratios are high enough that the % health damage from liandrys won't out damage AP items until the enemies have enough health to make it worthwhile. Combine this with the fact that W already does % health damage. I would say liandrys is a solid 5th item that you usually want around when big team fights start happening. However, you can get it earlier if you're against a tanky laner or jungler, the team has multiple tanks, or you didn't get fed enough early game and you need late game damage. Even if you get an early haunting guise for mpen, you should usually wait to upgrade it.
I rarely get to a 6th item, but I usually get zhonyas. The AP plus active is probably the best option. If you get in trouble, blow all your spells then activate and watch the dps tick while your spells and Voidlings kill everything. Ludens is probably viable, but I haven't tested it enough.
I also really like spell vamp on Malz, but I think it delays his build too much. The sustain is great, you never get forced out of lane, but you delay damage items. Will of ancients could be a viable 6th item in certain games.
Those are my general thoughts about Malz builds, let me know if you agree or think differently!