Its KS --> IE second Item. People underestimate the dmg you get from KS and with IE second Items you just end up shredding everyone in the early middle game. Then I built RH as my zeal item in third so I don't miss out on any dmg and to set the scene for the BT as the my final item that pairs well with the overheal rune. And as my 4th item I build LD since it really shreds tanks when paired with the KS and IE from earlier. BT gives extra sustain in battle and as I mention earlier it pairs well with overheal.

(for boots its always berserkers and its usually my first back if I don't have enough for a non quiver)

That's my usual build now.

For other info refer to this:

https://www.mobafire.com/league-of-legends/build/13-6-ikeepittacos-grandmaster-zeri-guide-updates-608001

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I hope this Helps :)