Long post, but totally worth it.
There are other, less gym-oriented exercises for explosive speed. Before I say them, I agree that squats and deadlifts are the best way to gain muscle in the areas that you need...But...
They don't promote the explosive speed you're lookin for; a proper squat isn't exactly done at the same speed as in tennis.(also it doesn't train 'white muscle fibre' or whatever it is)
It's abit raw, but the technique that I used(former tennis player #8th in province) is pretty simple. I found a box about 1.5 ft tall and 1.5 - 2ft wide and practiced jumping over it sideways.
If you don't get it, ill try to explain it:
1. Stand about 6inches away from the box, and have it on the left side of you, so you could lean down and touch it with your hand.
2. With your feet together, use both feet and jump over the box, landing with your feet together. Work to keep proper form on the landing(ie no arm flailing after your feet hit the ground)
3. After getting the hang of this side-to-side routine, start using each landing as the spring for the next jump.
Doing this in a routine and rep/set format should give you that explosive power you're looking for. Even try to speed it up so you're going back and forth as fast as you can. You will definitely notice the change within acouple weeks.
4. Pretty simple eh? After awhile you may feel this exercise is too easy. The next level is to do this drill with 1 foot only(outer foot from the box). Use the same principles as with 2 feet.
After you get proficient, try mixing it up, like jumping to the front of the box instead of the other side, then the back, etc..you know, be creative!(afterall you're not always going to be moving directly side-to-side. Even try carrying a couple dumbbells while doing this drill.
My coach taught me this drill a long time ago, when I used to play competitively. It's a drill formerly taught in rugby and football for sidestepping with explosive speed.
Best of luck on your mission to wimbledon m8, follow the dream!
To recap: Squats and deadlifts train overall strength but aren't enough to create the type of movement(lightning fast) i'm guessing you want.
