This is a purely offensive build for Xin Zhao, and I use it quite often. It provides four key aspects speed (both movement and attack), critical strike, and life-steal, in addition to reasonably high damage. I also have a Tanky DPS build that I use that switches out one Bloodthirster and the Infinity Edge for defensive items, usually a Warmog's Armor for health and either a Thornmail for primarily AD teams or a Force of Nature for primarily AP teams,(There are special cases in which a single character can affect my decision, such as Master Yi who is hailed for his speed, will generally direct me to buying a Thornmail, even if there are some AP users).

This build may seem cheap or worthless to some people, and they may be very correct, however it works for me personally and the build isn't everything, if someone fails while using a certain build it is more than likely not the build, its probably the person not being skilled enough to efficiently use the champion.

Pros:
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Fast attack speed
Reasonable survivability with lifesteal
Respectable damage with crit

Cons:
Few escape mechanisms (except ghost)
Somewhat squishy (when not building Tanky DPS)
Susceptible to stuns and focusing

Many people would consider this selection of items to be noobish or unskilled. However my philosophy is use what you have and can get to get what you want. I follow this build in about 80% of the matches I play with Xin Zhao and am generally pleased with my performance.

I do try to buy the items in this order, unless I feel I need one more than the others, though I will usually not buy the Infinity Edge until I have at least the two Phantom Dancers.

The runes I use I actually found on an older build, that I used for a while. I find that the armor pen is almost a must on AD champions, though it isn't necessary to have quintessences with armor pen, as there are other quintessences with more useful stats, I just personally prefer them. The attack speed runes are there not only to give you a boost in the beginning but it allows Xin Zhao's attack speed to cap at just under 2.2 which is quite good. Lastly the ability cooldown I find very useful in combination with Battle Cry. It allows for more TTS, AC, and Crescent Sweeping, it basically allows for more of everything, especially ganking.