locking the side/top/bottom view to prevent accidentally change it to perspective

Hi when i’m in side view or top/bottom, i don’t want to be able to rotate view so accidentally will become perspective view. I can do this by turning on ‘lock’ check box below the ‘toggle quad view’ button, but the problem is now i only can pan/move view. In fact, I want to be able to pan and zoom like any other 3d app in general. How can i do this with ‘lock’ is active ? any hotkeys to setup ?

sorry solved, the hotkey (zoom view) has been accidentally removed when i switch to maya hotkey. I add ‘zoom view’ and problem solved.