Right clicking is usually for context menus. Double clicking would be ok for zooming in.
(As a rl UX dev) I made a post about UI problems to EA forums which included suggestions for zooming in/out. I'll copy part of my post here as well.
Add a breadcrumb (preferrably to upper left corner) which shows you currently selected Server/Kingdom/Duchy/County. You can use the breadcrumb to jump straight from County level to Kingdom selection. Remove "Go back to..." -button from top of info panel. If breadcrumb is added, server selection can be removed from the bottom left.
Choosing an domain and then clicking Look inside -button in the info panel is a clumsy way (too much mouse travel). Using double click or mouse wheel zoom on currently focused domain is more modern way. Mouse wheel could also be used to zoom out.
Speaking of "mouse travel" etc might sound silly, but in making a smooth UI removing these unnecessary actions is essential.