A problem with z3ta+

In FL Studio, often having more than one instance open of a CPU intensive program means it slows down, or distorts the sound. Sometimes it sounds like a "click click clicking" in the background. Basically,either your pc needs updating, or Z3ta (i’ve never used it) is CPU intensive and only mean to have one instance open. If you record your track in the finished mp3 or whatever, the clicking and distortion isnt there.

If it is the lack of processing power as described by tilldeathdousparty, you can always alter the quality mode of each instance, eg the default quality should be "standard" or something like that, it can be set to "draft" I think, it won’t give u the same quality of sound but you will be able to run more instances, and change the quality back before you render.

Are you using ASIO?

If you don’t have one already pick up at least a semi professional audio interface. M-AUDIO makes some really good stuff and so does Presonus. I don’t know abelton exactly but alot of daw programs have a track freeze option. This works to help when working at low latency’s. Essentially it renders a temporary mix for that vst and unloads it from your cpu. If you need to change the sound of that vst later, you can unfreeze and freeze what you already like in the rest of your track. Once again this is a very helpful option when you need to keep a low latency setting. For example when recording your parts. Otherwise once everything is tracked and all hands on automation is complete, go ahead and crank up the latency in your audio driver before starting your vst host.