GNUPLOT cannot zoom in

Zooming and unzooming isn't possible in interactive windows which are left open with the -persist flag. Those operations would require a redrawing which isn't possible anymore since the main programs has already exited.

Quoting from the persist documentation:

[...] gnuplot will open a display window, draw the plot into it, and then exit, leaving the display window containing the plot on the screen. Depending on the terminal type, some mousing operations may still be possible in the persistent window. However operations like zoom/unzoom that require redrawing the plot are generally not possible because the main program has already exited