Dropdown menu based on the ZEN theme

Hello!

I created my theme based on the ZEN theme following theming lessons.

Everything turned out great. But now, when I install a module for the dropdown menu, I see two lines of the menu.

One is the one I wrote according to the lesson, and the other is an identical dropdown.

When I start editing the first one, the second one changes as well.

Can you please advise how to remove the display of the old menu?

Thank you in advance,

Eduard.

Screenshot: http://prntscr.com/1hzb2n