Is the Ziadrive a clone? The Zia symbol is the state symbol of New Mexico, but they got it wrong on the pedal. Just something I noticed. Didn't know it was a Zen clone.
Having owned both, I can say with some authority that these two pedals are not at all alike. Zendrive is a smooth, somewhat compressed, low-to-medium gain overdrive, best suited for playing single-note solos. The Zia is a low-gain, crunchy overdrive best suited for Stones-ey rock 'n roll rhythm guitar playing. The Zendrive has a bit of bass loss, while the Zia has, IMO, too much bass response, and can sound a bit flubby and raw.
I won't comment on the Zendrive, but I will say that I was not too impressed with the Zia I had owned. It got replaced by a barber LTD SR, which I think does a far better job doing the low-gain crunchy rhythm guitar (and also slightly overdriven leads) thang. With all due respect to Durham Electronics, however, I do own their SexDrive (clean boost with subtle compression) and that thing is never leaving my board.
they are the same size, run on batteries or a power supply, have an input jack & output jack, are designed for electric guitars, can be adjusted for volume & tone.
one is true bypass
one is not
one is uncompressed
on is not
one is designed for rhythm playing
one is designed for lead playing
both pedals share the same initials
both pedal builders have the same first name initial