On malzahar:
Learn to farm with aas. Once you know how to do that, you can use your e on minions only when you expect to be able to bounce it to your opponent. That will let you freeze lane and zone much more often.
What I mean by that is, you can auto each of the casters once, then place and e on the caster opposite of where your opponent will be. That will make him feel like he can walk up to last hit, because there are 2 minions the visions must bounce to before hitting him. But you can Q to instantly make it bounce to your opponent, still land the Q on him, and gain a ton of mana back all at the same time. Just make sure your Q hits them in order (from the side the visions are on).
Learn to manage your voidlings. Starting Q will let you get your voidling out much earlier (charge passive 1-2 times in fountain, use 1 q on leash), which is super strong. Any time you have a voidling out, the enemy shouldn't be able to get in exp range of minions. if they do, just aa them and your voidling will chase them out of lane.
Any time you know the jungler isnt there and you have mana, you can zone your opponent out post 6. Try not to push, that will draw their jungler to you. If the lane is pushed, don't try to last hit with aas, it's WAY too risky. Just use e, q, and voidlings to try to farm, and get back to safety as soon as you can.
If you need more info let me know