Is usb reclocking necessary?

No. Only unclocked USB signals need to be clocked. With modern clocks reclocking is unnecessary. 

If you want to fidget with your system get a turntable.

The innous reclocker is a good device and will make any dac sound better

We have a huge selection of dacs and the Phoenix did make an noticable improvement

We now sell servers which include seperate sound cards and clocks
So we don’t need any such devices as it is built in

Dave and troy
Audio intellect nj
Importers 432evo music servers

I would urge you to find a dealer that will allow you to demo a Phoenix USB in your current system to see if it improves sound quality enough to justify the cost. In my system, the Phoenix improved the realism and naturalness of the music supplied by my Innuos Zen Mk3 and processed by my PS Audio Directstream DAC.

I liked that the Phoenix was designed to work perfectly with my Innuos server and included a clock, a high-quality power supply, and a USB regenerator in the same case rather than expecting me to cobble together several external boxes and power supplies. This is basically the same approach as Innuos took in designing the USB path for their top-of-the-line Statement server. The fact that you already own a Zenith server makes the Phoenix a logical upgrade path for your system. But you really should demo it first to make sure that the sonic improvements you hear are worth the cost.

@mijostyn says:

No. Only unclocked USB signals need to be clocked. With modern clocks reclocking is unnecessary.

Well, that appears true on the surface. And most people don't specify enough configuration data to rally know. But let me be very clear: with systems running with the source as slave and the DAC as master (clocking), and with stuff that was considered well-clocked when it was new, adding a USB interface with isolation and re clocking has made a huge difference several times.

Note that my data point is NOT a box in the middle, which brings its own can of worms, but a replacement of the coaxial SPDIF provided originally with a custom PCB with independently powered (line powered) USB; full ground, signal and power isolation; clean power to the processing stage, and tight clocking beginning with a read buffer --> then spit out to the DAC.  Yes I'm being a little vague.

So while your point is well taken it comes down to "how well is the internal clocking/timing implemented?", "how dependent is it on source timing?" and "how good is the magic box being added".

I tend to agree that i would NOT just add a magic box.