Zephyr has never really been a top-tier Warframe. She had a lot of utility as the "flying Warframe" when she was initially released way back update 12.0, but that utility disappeared almost immediately once Archwings were added to the game.
Since then, Zephyr has received a few minor tweaks to give her abilities some added utility, but they never really allowed her to compete with other high-mobility crowd control Warframes like Nova.
But that's about to change in a big way. Along with yesterday's announcement of the big Railjack rework comes this smaller announcement from everyone's favorite Digital Extremes employee, the Warframe whisperer himself, Pablo Alonso.
Along with update 29.10.0's new Railjack experience, everything about Zephyr is about to change (except for her Turbulence ability, which was her only great ability). Tail Wind now does almost ten times as much damage during a dive bomb at max rank and also includes a hover-mode if you press and hold the ability key. This synergizes well with Zephyr's newly added passive ability that grants her added crit chance whenever she shoots while in midair.
Airburst used to be a poor damage ability that just knocked enemies outward, which was often detrimental to Warframe's gameplay. Now, Airburst instead draws enemies into a single point, lining them up perfectly for an AOE explosion, penetrating weapon fire, or a swipe of a really big sword.
And finally, Tornado has been changed so that it starts fully-formed without the need for Tenno to waste energy powering it up with Air Bursts. It can be toggled between "stationary" or "roaming" mode depending on whether you cast it on an enemy or not, and enemies get consistently sucked in rather than thrown around the battlefield.
On top of that, Pablo also showed off a sweet new aviator-style skin that'll hopefully arrive along with the Zephyr rework.
Still no word on when update 29.10.0 will drop, but in keeping with previous updates, it could be any day now.