Which zone has most potential for variety?

I was wondering and thinking about the different zones. I lived in Hawaii and loved the year round gardening it was awesome. I also loved the bananas, mangoes, and fresh coconuts.

Although some fruit and veggies from colder temperatures are also great.

I was thinking what would be easier/ simpler; to make a cold zone warm or a warm zone cold. I am not trying to make it snow in the desert, but to create a huge variety of plant life in a certain area.

I would think it would be easier to make a cooler place warm, but thats just a guess. It seems that the more diversity is in a system the healthier it would be as a whole. A zone around 7-9 seems to be ideal for great diversity, but i dont really know, there are a lot of factors

A Mediterranean climate in Zone 9 probably gives the most possibilities for different kinds of plants.  Somewhere it gets neither too cold nor too hot, with a good amount of sun.  One can grow both temperate and subtropical fruit in such a zone, with possibilities to grow tropical fruit as well. 

H Ludi Tyler wrote:
A Mediterranean climate in Zone 9 probably gives the most possibilities for different kinds of plants.  Somewhere it gets neither too cold nor too hot, with a good amount of sun.  One can grow both temperate and subtropical fruit in such a zone, with possibilities to grow tropical fruit as well. 

Thanks Ludi