google maps used to have the +/- icons in the corner of a screen.. I found this to be very useful for single hand operation of maps... double tap + sliding do

google maps used to have the +/- icons in the corner of a screen.. I found this to be very useful for single hand operation of maps... double tap + sliding doesn't work too well because your slide action is constrained to the range of your finger movement, and typically results in a small amount of zoom.