I was wondering if Furor or Rage (from Phage, TriForce, and Black Cleaver) stacked with the % movement speed bonus on Zephyr. Please help :P
Yes it does stack but it may not be intuitive in the way that it does so.
If the name of the Unique Passive is different then you can be sure that they will both be applied to your champion.
Furor's unique passive is called
Furor and as you've pointed out the unique passive of Phage, TriForce, etc. is
Rage. As the names are different they will both stack with each other.
However getting a Phage after already having a TriForce will not further increase your movement speed when hitting with your basic attacks. The same applies if you get multiple Phages.
Zephyr's movement speed increase is not a unique passive, so it will always be applied.
More information on how they stack:
Movement speed is calculated with the following formula:
(Base Movement Speed + Flat Movement Bonuses) × (1 + Additional Percentage Movement Bonuses) × (1 + First Multiplicative Percentage Movement Bonus) × .... × (1 + Last Multiplicative Percentage Movement Bonus) × (1 - The Highest Slow Ratio × Slow Resist Ratio)