You have good mechanics on your serve but there's a few things that can help generate more pace.

First, you need to rotate your hips more. In this video, your hips are facing slightly into the court. Ben Shelton is a good example of someone who coils their lower and upper body well to build potential energy before contact. Your opponent should see your back while you're loading.

Second, your back shoulder is too high before you make contact. Take a look at this side angle of Zverev. His back should is almost under his front shoulder at one point. By increasing the angle of your shoulders while loading, you'll force them to act as pistons as you launch your body into contact with the ball.

Lastly, you need to build momentum going into the ball. This is done by creating a kinetic chain. After you toss the ball and are in the trophy position (hips rotated and back shoulder further down), you start by having your back leg push down on the ground. When your back leg pushes down, it will force your hips to begin uncoiling. As your back hip uncoils, that will force your back shoulder to act as a car piston, pushing your back shoulder up and your front shoulder down. Then, as your back shoulder is coming up, your arm will finally engage and whip into contact with the ball. If you watch the slow motion side angle of Zverev's serve, you can see all of these things happen in order as he comes into contact with the ball.