How to Pinch Zoom on device with no touchscreen, like an Android Stick?
I just found this info with a quick google http://www.pcworld.com/article/184656/android_keyboard_shortcuts.html

I hope it helps.

Android Keyboard Shortcuts: Browsing

• Menu + I: Zoom in

• Menu + O: Zoom out

• Menu + J: Go back a page

• Menu + K: Go forward a page

• Menu + R: Refresh current page

• Menu + F: Find on page

• Menu + B: Open bookmarks

• Menu + S: Open social network sharing menu

• Menu + H: View browsing history

• Menu + S: Open browser settings