I suck at defense lol
Mix it up but don't get too complicated. Stick to your core things that work well for you and build counters off of them. If you like a certain blitz, sometimes shift your D to the blitzing side to overload that side of the o line, next time shift away from the blitz. It tricks the QB to run away from the shift, therefore flushing him to the blitzers.
And when you run zone, hide it from your opponent, people will gash zones when they see it before snap. You can come out in man 2 under and audible to zone before the snap. Or if you use a lot of Cover 3. Cover 1 man looks very similar and is a good change up play call.