---

Level 1
In my opinion the best talent to go for is Greater Cleave since the range of 33% allows you to still keep a little bit of distance to your target. it allows you to trade safe at level 1.

---

Block can be good against Nova but in most of cases it won't matter since it only has 2 stacks.

Rapid Displacement is an other option to start with, it gives you alot more mobility what is quite strong against combinations with high cc.

Regeneration Master is a Talent that you won't feel in the early game. It also shouldn't effect you much more in the lategame since you want to do quick trades.

Seasoned Marksman is a Talent that highers your Basic attack damage. If you play on autoattacks that is great, but since Zeratul scales better with his skills, we can ignore it.

---

Level 4
Gathering Power increases your ability damage for a maximum of 20% this means you will deal the initial burst that your looking for. Also it's a quite strong talent specially for roamheavy characters like Zeratul or Nova.

---

Focused Attack allows you to deal 150% damage with every basic attack after 10 seconds or less depending on the amount of basic attacks you do.

Vampiric Assault lets you heal for 15% of your dealt damage. That sounds alot, but since you lose atleast 8% damage it's no option for me.

Sustained Anomaly is a Talent I tried quite often. It has potential to be usefull but thats only if your enemy is grouped up at the same point. Thats basicly the only moment it is usefull. Most of the time you will feel the missing damage on a single target.

Vorpal Blade is an mobility Talent that allows you to go back to your last target. Since it only works within the last 3 seconds it is useless since you go in to deal the initial burst and your cooldowns are higher then 3 seconds, meaning you will lose damage.

---

Level 7
This is situational. I mostly prefer Rending Cleave since it makes you even more anoying and you can deal alot more damage as you possibly can do with Shadow Spike, but Rending Cleave very weak against heals or shields ( Uther, Tassadar, Rehgar,...).

Shadow Spike is the other option you have, it's really strong for escaping or poke + it can be placed as a zoning thing.

---

Follow Through is a talent that needs you to do basic attacks. You will not lose (alot of) damage if you take it but your life will be alot more risky.

You don't need First Aid since you will either get shut down instantly, or kill your target. It still might safe you sometimes.

Searing Attacks is a talent that needs you to stay in the fight and do basic attacks. Since you want to be mobile it is really bad for you over all.

---

Level 10
Void Prison can be used in teamfights to cc the enemy frontline to get rid of their cc, or it can be used to cc the backline to get rid of the damage. Since Zeratul's synergie with autoattacks is really bad (his basic attackspeed is really low + his spells do more damage if you skill them), Void Prison is the only logical option. It has also the potential, to turn fights completly. Remember it can also be cast onto your or the enemy Core.

---

Shadow Assault is pointless since you don't want to basic attack through your fight. It still can enable you to deal the little amount of damage to kill an opponent but on high risks and you will get destroyed by safe cc.

---

Level 13
Wormhole is giving you great mobility that you can use for jukes, stealing coins/seeds/skulls. It also enabels to use the blink offensive without getting caught.

---

Giant Killer aswell as Assasin's Blade need you to do basic attacks. This means you have to expose yourself + you can't take Wormwhole you lose out of alot of mobility.

Burning Rage needs time to do damage and is a bad talent for a Hero that wants to deal initial burst.

Spell Shield can be usefull against other skill based heroes, however you lose too much mobility to take this talent.

---

Level 16
This one is your biggest powerspike in the game, once you have Double Bombs your damage is going to be insane. In a lategame scenario this means your bombs can deal up to ~1400 damage. Defenitly the strongest talent to pick.

---

Executioner, Void Slash, Stoneskin and Berserk will ever give you as much damage or utility as Double Bombs will give. Stoneskin gives you more tankyness, but since your basic health isn't that high it will not matter and gets defenitly outscaled by Double Bombs.

---

Level 20
Bolt of the Storm allows you to be even more mobile and anoying to everyone on the enemy team, combined with Wormhole it gives you great chase- and jukepotential. Protective Prison is an option, but I don't really like it because your teammates usually should never run into the Void Prison if its not needed. Also you are unable to defend your core with the Void Prision anymore since its an allied structure.

---

Fury of the Storm is pretty useless since you will never deal enough damage with basic attacks to make it relevant + the enemys usually won't stand that close to each other.

---

Gameplay
Make sure you allways look for an oportunity to gank other lanes. Roam as much as possible in order to get your team ahead. Your team still needs to be in lane to get the EXP so make sure to communicate with your team. Your damage really high, but it needs alot of body blocking since your strongest point in the game is when you reach lvl 16-20.
Zeratul is an assasin as far as you can call an assasin out. His stealth enables him the chance to get into the backline of the enemy team and slay them. Also it allows you to walk arround in the enemy base without turrets (not the core) shooting you. It allows you to snipe Abathurs for example. But I can'T really recommend that in the early game because you won't be able to have too much profit out of it, and its really risky. Once you understood his mechanical play you gonna be able to slay your way through your enemys.