Mandelbrot zoom problem

Hello. Im working on a Mandelbrot program using GLUT. i have the user click on two points which forms a rectangle for zooming in. i then translate the pixel coordinates to my own coordinates (initially x=[-2,2] and y=[-2,2]. after about 2-4 zoom-ins i get funky lines and the coordinates are really close together. i can’t seem to fix it. maybe a rounding error? any help would be appreciated.

Jeremy Kolb