I really like Malzahar but he needs some quality of life changes.
Passive Summon Voidling:
The voidlings have no reason to scale off of AD. instead their damage should be reduced and then given a small AP scaling aiming to result in the same amount of damage until very late game. Also where they spawn should be clearer. Having them spawn between Malzahar and the nearest enemy champion would make it predictable and make it easier for Malzahar to spawn a voidling to block a skillshot. Also to improve the voidlings movement they should have no unit collision making it so that they can move to their target easily and also prevent Malzahar from getting stuck on a voidling that doesn't know what it's doing.
Q Call of the Void:
The animation should be clearer about what it is going to hit, as it is now it looks thinner than it actually is. Also the cast time should be reduced to make it easier to hit a surprised enemy with all four of your spells before they flash away. Also the vision it applies should be given to the entire area that it effects instead of just the two ends so that you can check a brush without having to face a specific direction.
W Null Zone:
This needs to deal damage every half second instead of every second.
E Malefic Visions:
Reduced cast time and maybe a 50 range increase so that it has the same range as his ult.
R Nether Grasp:
For his ultimate I feel that if you use a spell while casting your ult it should not interrupt your ult. Instead it should buffer and be immediately cast after your ult has finished. This would allow you to use ignite even if you aren't in range making Malzahar move into range after his ult finishes. This would also make it so that if you accidentally press Q>W>R>E instead of Q>W>E>R you will just wait to cast your E until after your ult instead of interupting your ult to use it. This change wouldn't stop you from interrupting your ult by moving.
These changes wouldn't really change how strong he is it would just make him feel better to play. However if these changes do end up buffing him it would not be unreasonable to reduce his basic attack range and/or reduce the silence duration on his Q.