I just learned this and figured I'd share. You can skip the intro movie and open the game to the main menu, where you choose your parks.
- Open your Steam Library and select the Planet Zoo game
- Right-Click on the name Planet Zoo and choose Properties
- On the properties window make sure you are viewing the GENERAL section on the left
- At the bottom under "LAUNCH OPTIONS" type in -nointro (make sure it has a dash to start and no spaces anywhere)
- There is no Save button so once you have -nointro typed in, you're done. Use the little X in the upper right of the properties window to close it out.