Hi.
In Skyrim instructions it says press 'Z' to shout..
yep , that works..

BUT NOWHERE does it tell how to combine shouts.

For example, when learning to combine the Word of power from borri with my original shout, i had to Guess how to do it.
I HAD TO PRESS 'Z' & 'X' AT THE SAME TIME.
That royally svcks.. And was just a lucky guess.

However, the next shout I need to learn is the whirlwind shout..
And ive no idea how to activate it.
Please help.

Am I dumb, Or is skyrim's instruction manual incomplete?

Combine shouts? =S

Hold down Z for longer. You can't combine shouts, you can say more than one word of the shout to make it stronger by pressing and holding the button.