When it comes to Zul'jin people shy away from any build that involves Guillotine and instead prefer the auto attack Taz'dingo! builds. Granted, those builds are safer options especially in competitive games. However, where is the fun in that? Where is the challenge? And where is the satisfaction of landing a perfect killing blow with a long ranged skill-shot?
If you want answers to these questions, you came to the right place!
In this guide I will explain how and why I prefer to play Zul'jin, as well as TALENT SELECTION and GAMEPLAY TIPS. But first the PHILOSOPHY!

Don't get me wrong, I love myself some Taz'dingo! action with massive damage and rapid axe throwing, but the Guillotine always sparked my interest since Zul'jin was released. This type of a build is usually referenced as "Spell'Jin" and for a good reason. More or less you will find most "Spell'Jin" builds to resemble my 2nd build here: Guillotine with Twin Cleave. The other option is the one I personally prefer and it is combining Guillotine with Grievous Throw. That way you also get some AA value from Grievous Throw, with the main focus on Guillotine of course. More on that in the talent section.
I've already mentioned that I prefer this Zul'jin style over others. You will try to constantly keep yourself on low HP so you could burst someone with Guillotine. Not having that god-save with Taz'dingo! will keep you on your tippy toes. I find pleasure in such a challenge and it keeps the gameplay interesting.
All that personal stuff aside, these talents have great synergy and actually make the build viable - it isn't just some troll build you know (pun intended).

Level 1

Boneslicer Generally this isn't a bad talent, but considering the other two in this tier we are going to skip it. We won't be focusing that hard on auto attacking to make the most out of it.

Recklessness Going down below 75% of max hp with Zul'jin is quite easy (especially with Amani Rage), and thus that sweet +10% spell power will be active most of the time. Plus, that 20% attack damage increase isn't a bad addition either.

Headhunter NOTE: The link is for the old Headhunter which would've been interesting to have. Now it is a quest that will add +2% damage for every 1st takedown on an enemy hero.
After getting 10% (or 5 hero kills) you get 1.1 bonus attack range. Like Recklessness it has a double effect and they are both good for this build (we obviously aim for that 10% damage increase, but the range comes in handy as well). If you plan to go for this instead of Recklessness then consider to arrange those takedowns with your team as soon as possible.

Level 4

Troll's Blood A good pick if you are harassed hard or without a healer. Increased effectiveness of healing as well as additional Mana restoration is a great bang-for-the-buck. Again, go for this talent if you are forced to play more defensively - or if the support sucks! Otherwise go for Voodoo Shuffle.

Voodoo Shuffle A defensive talent, but with more utility. This talent will provide less healing than Troll's Blood - but reduced Mana Cost and cooldown of Regeneration allows for more frequent usage. Troll's Blood restores Mana and that restored Mana can be used for other abilities, while Voodoo Shuffle only reduces mana of Regeneration. However, the active effect is what makes this talent so powerful - both for escape and engage. So go for this one if you are against a cc heavy team.

Amani Hide Zul'jins latest change was the inclusion of Amani Rage into his basic kit. Because it was such a popular talent (for obvious reasons!), it managed to find its place in many builds. That made other two talents in this tier worthless (more or less). Now this tier isn't a no-brainer anymore. Tables have turned and this talent, although viable, seems to fall short compared to Voodoo Shuffle and Troll's Blood.

Level 7

Vicious Assault Go to talent if you prefer to use Grievous Throw over Twin Cleave. Not that it isn't of much importance whatever you go for. As mentioned, I prefer it this way. Less mana, shorter cooldown and it is easier to land - suits me just fine. Don't forget the value from Grievous Throw combined with No Mercy! and damage acquired from You Want Axe? ( Berserker).

Arcanite Axes Go to talent if you prefer to use Twin Cleave over Grievous Throw. A steady damage increase without a cap. You will be limited only by your skill to land a hit (which isn't that hard). Combined with Wrong Place Wrong Time it can deal absurd amounts of damage! A true Spell'Jin right there.

Ferocity I could see this going well with Let the Killing Begin, but in order to get the most out of both you would need Taz'dingo!. Since we are going for the Guillotine, I guess it is clear why not to choose Ferocity.

Level 10

Taz'dingo! NO!

Guillotine YES!

Level 13

Lacerate This is generally a "mobility" tier. The slow is nice especially if you land both axes, but it is nothing compared to Ensnare!

Eye of Zul'jin This one has some value. It goes great with Grievous Throw, allowing you to chase and land as many attacks as possible. I'd go for this one for sure if it weren't for Ensnare.

Ensnare YES! It's that good - in reality it is the only talent in this tier that will help you to land a perfect Guillotine. Plus, it is a secondary ability, thus it is free of cost. Apart from the combo with your heroic, it can serve as a way to escape and set up skill shots for your other teammates, the possibilities are endless...

Level 16

No Mercy! I'd say this is one of the key talents for any auto attack build especially vs armor heavy team. For our build it is suitable with Vicious Assault. Not much to say about this one: even if you go for the Grievous Throw orientated build you can still pick Wrong Place Wrong Time. I prefer it this way.

Wrong Place Wrong Time This one on the other hand has a greater synergy with its level 7 talent Arcanite Axes. With You Want Axe? from Berserker you can land a second hit. I wouldn't mix this with Vicious Assault although it is a minor preference so take what you feel is needed for a given situation.

Eye of Zul'jin A good talent, but given the other two options - it gets overshadowed.

Level 20

Amani Resilience Legit **** right here! Obviously, it is unavailable.

Buzzsaw This will grant a chance to still hit even when initial hit misses its target. Plus, if you last hit you will get that full healing. Just to make sure it is clear: HEALED TO FULL HP. This is great for a clutch heal scenarios. Also it will keep you in the fight until Guillotine refreshes.

Forest Medicine NO! (to be fair it is a descent talent but why would anyone pick it instead of talent upgrades for heroics, considering how good they are?)

• You are still a fighter. Don't rely only on cooldowns. Berserker is your best friend.
• Guillotine is excellent to last hit (especially with Buzzsaw) but don't be afraid to start the fight with it.
• Be unpredictable: use your Guillotine while in fog of war. Pray on targets that have LOW HEALTH POOLS so even if they are around full HP you can still nuke them!
• Once you get Buzzsaw you can aim the Guillotine to hit while it rolls. Makes it more unpredictable. It does deal 75% of initial impact damage but if you are low enough those 75% are still a lot of damage.
• Although Zul'jin is a fighter, without Taz'dingo! don't be overly aggressive. Remember you have range with Guillotine, you can land kills from a safe distance.
• Pay attention while on low HP: hunter can become the hunted. Dancing between life and death is pointless if you don't land that Guillotine.