To zoom a sequence in the Sequence zoom view you can use one of the zoom button on the sequence toolbar:

     <img src="/wiki/download/attachments/17465997/Zooming Sequence.png"/>

There are standard Zoom In and Zoom Out buttons. Additionally you can zoom to a selected region using the Zoom to Selection button. To restore the default view of the Sequence zoom view (when the sequence is not zoomed) use the Zoom to Whole Sequence button.