Overview
Zhask basically a midlane hero that has a weak pick rates but he could be powerfull if you know how to use it he is actually good at laning phase just by using his first skill.
Strengths
Good at laning, has good burst and DPS skill, has mobility skill (the ultimate), has CC skill (combo skill 1-2), has slow (third skill), and also has high survival rate at teamfight especially when mid/late game by using his ultimate to run or protecting teammate.
Weaknesses
Weak team fight for early game and less damage than the other burst mage
Burst late game
Use arcane boots for magic power and penetration, Sky piercer as optional item, glowing wand to lowering enemy's heal and shield gain, holy crystal for the best magic power, divine glaive for 40% penetration but it was an optional item to you can change it to magic wand if the enemy's squishy, lightning truncheon for better burst damage.
Sustain dps
Cause Sky piercer is an optional item you can change it to blood wings for better sustain
High burst zhask
Magic emblem is the best emblem if you use burst zhask with the cooldown reduction, high magic power and penetration from the magic emblem with first emblem talent is rupture to get more penetration, second talent weapon master to get more magic power from item by 5% and third one is impure rage to highly burst enemy by dealing 4% of target's max HP as extra adaptive damage
Fast item
Just change the weapon master to bargain hunter if you want to bought an item much faster
Sustain dps
Change the emblem to common emblem if you want him to sustain much longer at team fight without fear of running out of mana
Battle Spell
Zhask is conditional hero that can use many spell he could use purify, flameshot, or other spell but for me the best spell for zhask is flicker cause he could easily run from battle by using his ult and do a combo with a flicker that makes you run faster and keep you safe from gank.
Early phase
Don't be so rough at the early phase cause he has weak burst and DPS at the early phase and just focus at your laning to get level 4 but don't forget to roaming and joining a war for a little bit.
Mid phase
Focus on dealing DPS at the enemy by using skill 1 and skill 2 to stunts and dealing damage to enemy but be careful if you don't have ultimate don't be too offside and greedy to get kill
Late phase
Focus dealing burst, cc and slowing the enemy and use his ultimate to backup the back liner and dealing damage
Best With Sora
Zhask can be more aggressive if there's a tanking hero in your team but it'll be more better if it is a montage hero like sora, Gatotkaca, or terizla for the exp lane
Watch Out For Cici
Zhask can easily get caught by cici's ultimate that make him unable to move cause he was attached to his own skill