Can I leave put the lemon oil/extract and add more zest instead?

Hi there! You can definitely leave out the lemon extract. For future reference, here are some non-lemon lemony subs to consider: https://food52.com/blog/25168-best-lemon-zest-substitutes

You'll get plenty of lemon flavor from juice and zest already in the recipe.
For such a small amount of lemon oil or extract, you could just leave it out.
Or replace with same small amount of orange extract or brandy for some more complex flavor notes.