Zones correspond to naturally occurring conditions of a region. Generally these are applied to native species and elective agriculture and gardening can broaden the radius of each zone into more of an overlapped pattern. This is because we can artificially modify our environment to create man made ecosystems that are more accommodating to the species we choose to grow.
So dont despair if your dream plant isnt listed as suitable for your region. Instead list the variables present in its natural habitat and determine how to recreate those. For example a tropical species wont thrive in desert conditions due to missing variables like high ambient humidity for 1. However in a contained greenhouse, a humid environment can be replicated. Even without a green house, plants grown in clusters surrounding water sources will maintain a localized humidity bubble quite effectively.
Plants that are intolerant to a freeze can have their roots buried in active compost which will generate underground heat. The ground around their base can be covered in black fabric to attract sunlight and retain heat. Even trunks and limbs can be wrapped with black foam for insulation and capturing heat from the sun. It is less a matter of what you could grow, and how many modifications you’re willing to make in order to grow what you’d like.