Push the "!!!" button.

Why do you limit yourself to ".jpg" and ".png"?  If it is for publication in a journal or a book, you (and your publisher) will want the image in the ".eps" (Encapsulated Postscript) format which is "high resolution" by default.  In fact, "high resolution" makes no sense in EPS since it is a vector image format which maintaions100% accuracy at any magnification.

I am not aware of keyboard shortcuts for zoom and pan.  As you have observed, you may do them through the drop-down menu.  A quicker way is to use the icons that appear along the top toolbar.  Here is a screenshot:

Click on the red icon to zoom, the blue icon to pan.

Maple is cautious with fractional powers since a fractional power of a complex number is multivalued in general.  To reassure Maple of your intent, apply abs() to y(x), as in

de := diff(y(x),x) = 3*abs(y(x))^(2/3);

1. In mathematical formulas the parenteses (), brackets [], and braces {} tend to be used interchangeably, but in Maple they have quite distinct meanings.  Go through your worksheet and replace all [] and {} with ().

2. The Maple syntax for defining a function like f(x,y) = x^2 + y^2 is

f := (x,y) -> x^2 + y^2

You seem to use the notation

f(x,y) := x^2 + y^2

which is incorrect.  Go through your worksheet and fix those as well.

3. Your equations contain a parameter Gr sub zero, but you have given a numerical value to Gr without the sub zero.  Why?

> ListTools:-Rotate([a,b,c,d],1);
                          [b, c, d, a]

> ListTools:-Rotate([a,b,c,d],2);
                          [c, d, a, b]

> ListTools:-Rotate([a,b,c,d],-1);
                          [d, a, b, c]

with(plots):

odeplot(dsn, [t,u(t)], 0..tmax);

See ?odeplot for more examples.