@OK_Rabbit, note both mousewheel and ctrl+RMB scales both axes the same amount (ie zooms) while alt+RMB adjusts the scale of each axis separately, depending how far you move left/right and up/down.

However it's much easier to just press Frame or turn on auto framing using the Auto button. That fits all the curves to the size of the graph. Usually that is what you want but if it's not, often it only takes a little fiddling to get from there to the view you want.

Also note you can click the dots next to each row in the graph to control which curves are shown. This can help when you need to hide a curve that has large values so you can more easily work on a curve with smaller values.