One does not simply beat Malzahar in lane... with anyone.
Yes, that goes for AP assassins too.
You don't need to push lane 24/7, if you're aware of your passive stacks, you can keep very comfortable lane control, he farms pretty safely even without E if your voidling is up (also trades ridiculously well, the minute you throw an AA on the enemy, voidling does a lot of damage in conjunction with your E as well if you want to throw that in), and you just throw damage/last hit the wave at the middle, and if it's pushing, you either freeze it with said voidling, or E and kit it away to clear it up.