Operating system and graphics card
Short description of error
VSE Preview has missing menu entries (and shortcuts) that are avalible in UV/Image Editor to set zoom ratio.
I think the reson why they are disabled (in code) is becouse "bpy.ops.sequencer.view_zoom_ratio(ratio)" and "bpy.ops.image.view_zoom_ratio(ratio)" are inverted. For example "bpy.ops.sequencer.view_zoom_ratio(ratio=4)" gets me the same zoom when "bpy.ops.image.view_zoom_ratio(ratio=0.25)".