I've made a few purchases
I've made a few purchases from ZenPro now, and always appreciate their selection, unique item and mod offerings, fair prices, and (sadly now not-so-common) really great customer service. It doesn't get any better than great gear at good prices sold and serviced by friendly, helpful people.
I bought a ZPA 57 w/ the Oliver's transformer upgrade (from ZPA) a while back and like it so much I just bought another so I'd have a pair. The mic arrives in the factory Shure packaging with all the Shure paperwork and standard accessories that would come with a stock Shure 57. Aside from the tasteful “Z” badge on it to identify it as a modded mic, you can’t tell from looking at the mic that anything’s been done The mod seems to be very competently executed.
I got it to use on overdriven and distorted guitar amps and love that it provides an improved variant of the classic 57 take on an amp; it's basically what you'd expect, except it's already cleared up and less aggressive in the mids and given an appropriate, tasteful lift in the high end with no processing. I've also used it on snare and the Leslie of a Hammond organ rig, both with great results. Again, more of what you like & less of what you don't from a 57.
It's loads easier and quicker for me to set up and adjust get what I'm looking for with the ZPA 57 w/ the AMI transformer than a stock 57. I'm not a 57 hater anyway so, if you're starting out from a position of not liking 57s, it may not be a good fit for you?