These guides are a TL;DR version of my personally prefered way to play a hero. They do not claim to show the ultimate way to play the character (albeit possible) and they will not go in-depth on matchups, playstyle, tricks or every single talent.

Level 1

Block
Greater Cleave
Rapid Displacement
Regeneration Master
Seasoned Marksman
- All of these have enough merit to pick them
- I usually go with Seasoned Marksman, because it adds some damage, not much but it might be the few points you need
- It also synergizes with Searing Attacks

Level 4

Sustained Anomaly
- Allows you to block paths
- Even missed Spikes can now hit
- Often people run away if hit and into teammates, for each person hit that's a damage increase of 100%

Level 7

Searing Attacks
- Basically the same as Follow Through, but twice the bonus, for every autoattack not just the first after an ability
- Manacost is negliable (about as one ability)
- It has only 25 seconds cooldown
- It helps immensely with killing buildings, objectives and things like the Grave Golem on Haunted Mines

Level 10

Void Prison
- While Shadow Assault is not bad, this will help you win a lot more
- Allows you to CC a healer or other annoying people while you kill someone
- It has a really long duration
- Can help catch people
- Can freeze capture points
- Can make fights 3vs5 or better
- I guess you see why this is so good

Level 13

Wormhole
- Defensive choice, allowing you to blink in, deal damage and blink out instead of going in normally, which is a lot harder and riskier
Assassin's Blade
- Offensive choice, only take if you can actually stick on a target for a few seconds

Level 16

Double Bombs
- Synergizes very hard with Sustained Anomaly, allowing you to burst entire teams if they clump up, 1k damage is nothing to sneeze at
- Best option for single target damage (we don't go Shadow Assault, so Berserk wouldn't add as much damage and we don't want to stand there autoattacking most of the time)

Level 20

Protective Prison
- If there are a lot of melees on both teams this might come in handy
- Also if your team tends to walk into your bubble
- Most of the time this isn't useful because you will CC the enemy backline, not the frontline
Nexus Blades
- Passive damage and slow
- Its a simple buff to your damage, which helps especially with things you autoattack a lot (tanks, buildings, map objectives, bosses etc.)
Rewind
- Highest damage increase
- Especially good if you went for Assassin's Blade, because it's like a Wormhole with indefinite duration
- Harder to use
- Cooldown

Zeratul is an in and out hero more than any other. You are very squishy, but can do a lot of damage in a short time, after which you need to wait for your cooldowns again. Later in the game you can kill someone like Jaina in the 3 seconds of your Wormhole, partially because you have incredibly high autoattack damage and Searing Attacks scales well with that.

- Walk to your enemy use Singularity Spike and Cleave, then Blink out
- Instead of walking you can use Blink if you know it's safe or if you have Wormhole
- Use Void Prison to take annoying enemies out of the fight for 5 seconds (like a Lili using Ultimate or a Nazeebo)
- If possible, commit with Searing Attacks, noone does more autoattack damage than you in a straight up fight with Searing Attacks.