Open Zulu DJ.
Cick on "Add" in the bottom-left corner. Locate the two songs you want to mix, and select them. Drag and drop one song to Deck A and the other one to Deck B.
Play the song on Deck A by pressing the "Cue" button with a triangle on it. EQ the songs to your liking by sliding the "Bass", "Mid" and "High" filter with your mouse. Activate effects by clicking on the triangle button next to each specific effect.
Click on the "Sync" button underneath Deck B. Press the "Cue" button with a triangle underneath Deck B. Your tracks will now be mixing in tempo. Change the tempo on either by sliding the "Pitch" fader under both Deck A and Deck B.
Switch between the songs on Deck A and Deck B by sliding the cross-fader underneath the NCH logo in between both decks.