z3ta+ banks saved with versions earlier that 1.4 have issues when loaded into any version after 1.5.
The following banks were found to have problems in 1.5.3 and have been fixed: Bruce Rainier Cat9-1 Pads default_v13 EddoGQ MoreQuality Kire_Fat Analog Kire_Trancemania KvR Collab 1 KvR Collab 2 Llunasol32 Mattt Baka Disco Treats PSchelf Vintage and Dance Simesf Zeta BankF01 Speed 16Soundbank Speed NextLevel Trancebank (this is NOT 10trancebank)
This is a re-up of Bigtone's ATT bank anounced here - http://www.kvraudio.com/forum/viewtopic.php?t=58059 It is no longer available anywhere on the internet. I have contacted both Rene and Brok (aka Bigtone) about posting this bank here.
Revisited this oldie today. 5 instances, ~45 polyphony, all 2x oversampled = 30% CPU usage, which includes all insert effects. They don't make synths like this anymore. One instance of Diva alone reaches 50% at high polyphony.
It's not really fair to compare this to Diva. They use different ways to make sound. Z3ta is a wave table synth and Diva is a virtual analog synth that what I think recreates the circuits of an old analog synthesizer. That takes a lot more processing power. Also you can change the quality in Diva. But I agree with you. Z3ta is an awesome synth.