Pro Tools | First Main Windows : Edit Window : Edit Window Zoom Buttons and Slider : Vertical and Horizontal Zoom In and Out Controls
 
Vertical and Horizontal Zoom In and Out Controls
In addition to the Zoom control in the Toolbar, Pro Tools provides horizontal and vertical zoom buttons, and a zoom slider in the lower-right corner of the Edit window.
Vertical Track Height Zoom buttons (Edit window)
Horizontal Zoom buttons and Zoom slider (Edit window)