equations

Those constant zooms change the field size/image_width by the same proportion each frame. To find an unknown value you need to know the other 3. The equations are;

$proportion=1-(($small**2)/($big**2))**(1/$frames);

$big=round(sqrt(($small**2)/((1-$proportion)**$frames)));

$small=round(sqrt(($big**2)*((1-$proportion)**$frames)));

$frames=abs(round(2*(log($small/$big))/(log(1-$proportion))));

For calculating the x and y move in relation to the zoom.
distx = total of move x axis in pixels:
disty = total of move y axis in pixels:
distw = total change in width in pixels
Using the field size at each frame to calculate the x, y distance for that frame;
the equations are;

x=start_x+(distx/distw)*((current width-start_width));
y=start_y+(disty/distw)*((current width-start_width));