Hi, I can't really test it so here is my question.

Is there a way to create a Zoo Systém?

What I aim to create is to create a systém with other players (AI) that I won't have to bother with them as I would need just single fleet to blocade them all and if lucky most of the planest would be toxic or tiny :-)
I am evil I know... I just dont feel like genociding them all... or assimilating them.
I can do that with single race per systém by colonizing that area and then giving it to the other race and taking over their previous planets.

I can't test it right now so... is it possible like to have a systém where already another player is, get one planet there and colonize it and then give it via diplomacy to another player?

never really figured out what are the limitations on the giving planets in diplomacy.

One of the problems you will run in to is that when an AI race perceives itself as too weak, it surrenders to another AI race. SO especially if you are blockading their last planet and that planet is quite weak, a surrender is quite likely. Yes, but you can only colonize a planet in an enemy system when there are no enemy ships present, or if you have a NAP with them. Your colonies start with a single pop count of your own race, so you will have to send assimilated races to the planet manually if you want the population there to include alien races. Yes, but but you need to have contact with the race you wish to give it to, and friendly enough relations that they speak to you. Afaik the AI doesn't seem to move around assimilated population. So whatever the racial mix it is likely to remain the same once you give the planet away.