If you need Z1 sounds: buy a used Korg Z1 hardware unit ($500–800) and sample it.

A powerful physical modeling engine that mirrors the Z1’s deep synthesis structure. Arturia Pigments: While a wavetable synth, its "Utility" engine Comb Filters

If you search "Korg Z1 VST" online, you will find results. Be warned: 99% of them are clickbait, malware-ridden ZIP files, or fake "download now" buttons.

If you are looking to recreate the Z1 sound using other plugins, these are the key components of its to look for: The Korg Z1: A Hidden Gem that Changed the Game