Combining bibliography styles
Stick to one citation-style throughout your paper.

Do not combine different citation styles!

The pros of being consistent:


Paper looks nicer and more professional, i. e. like a real scientific paper
It's easier to read, because the text is not interspersed with different kinds of foot- or endnotes (reduced cognitive load)
Makes checking your sources easier


Cons of being inconsistent:


Some professors are quite allergic to inconsistent notation (I know of fellow students who learned it the hard way).
It gives a very bad impression


It wasn't understood how citations work and what their purpose is.
Perhaps, at least some material was just lazily copied from different sources (each using different citation styles) and you didn't do it yourself. Not the case, for sure, but you don't want to create that impression and have to prove your innocence. And it really looks like a good explanation for the strange mixing of different citation styles. 



In general, stick to one style. If you have been told which one to use, then use that one. Else, choose one you like (sometimes you are free to choose a style) or ask. But mixing them has no benefits, just downsides. In your case, use APA notation throughout your paper, just as you have been told.