Hey, not bad, however Zebra is easily the slowest of the 4 Heavenly kings a majority of his attacks are stated to be the speed of sound or sightly higher, Kazuma is in the 4 digit mach speeds as he was able to fly from Earth to outer space within seconds and then while clashing with Ryuho fly to another plan a few miles away from where he took of within a few seconds.
Here is a calc for the speed along with a video:
Let's start with a speed feat.
Speed Feat - Shell Bullet Ultimate/Stage 2
From 16:07-16:19, both Kazuma fly into space to at least the poin they break through some white barrier of light.
I just need a distance now, here's the scan I used to get it
See the curved white light? Kazuma and Ryuhou flew at least to that point in 12 seconds.
Travel Distance = 214 pixels
Earth Diameter = 3,033 pixels
Travel Distance/Earth = 0.071
Earth Diameter = 12,756.2 kilometers
Travel Distance = 905.690 kilometers
Timeframe = 12 seconds
Speed = 75,474 m/s or mach 220
Anime makes this far too simple.
Next up? Their Explosion Feat from episode 25.
Destructive Power - Proud Fist and Stage 3 Part 1
(If you can't view the video at your location just watch the first fight I posted)
This here is the completed explosion.
You'll notice it's peaking overtop the top curvature of earth.
In relation to that?
We see rather clearly in the second screen I posted that Japan at that time of year, in relation to the top of the planet's curve is a fair deal below said curve (you can track where japan is using the vertical large explosion kazuma and ryuho caused that episode. Japan's even visible, just looks white, but its clearly the shape of japan)
What's the mean? I can get my minimum explosion radius and flight distance given they flew into the sky perpendicular to Japan.
They're also easily a fair deal higher in the sky, given no ill effects of the explosion reach the ground below, and the explosion we see peak over the top of the planet isn't a full hemisphere, the majority of its mass is still hidden behind the planet.
Earth Diameter = 292 pixels
Fireball Radius/Distance Traveled = 40 pixels
Fireball Radius/Earth Diameter = 0.137
Earth Diameter = 12,756,200 meters
Fireball Radius/Distance Traveled = 1,747,599.4 meters
Fireball Diameter = 3,495.199 kilometers
That'd also effect the speed of Kazuma and Ryuhou's flight into space.
Speed Feat - Proud Fist/Stage 3
Here I used the radius of the explosion as the minimum distance they needed to travel in 4 seconds for the feat.
My radius here is 1,747,599.4 meters
1,747,599.4 meters/4 = 436,899.85 m/s or mach 1,283.904
Kazuma and Ryuhou's Episode 25 Explosion Yields = 138.743 teratons
Kazuma and Ryuhou's Final Battle Fireball Diameter = 3,495.199 kilometers
Proud Fist/Stage 3 Speed = 436,899.85 m/s
That would mean that Kazuma should be more than fast and strong enough to tangle with Zebra despite the Mt. Turtle feat. Even taking calc outs of the equation Kazuma and Ryuho were able leave Earth from that little amount of time as well. I din't want to take up too much space but I can link to the full calc if need be.
Now because Guyver cannot actually effect Kakyoin with his sound waves as Zebra would likely have him covered for protection Guyver still has access to his Gravity control; while Kakyoin can have the advantage with distance and his barrier, Guyver can still use it's mega smasher, a blast more than powerful enough to get through Zebra's shield and kakyion's barrier,
and because of the Guyver's sensory abilities it can detect all kinds of movements allowing him to be able to prepare for attacks he may not even be able to see such as Emerald splash or Zebra's sound waves. Also with his Gravity control he can create a small barrier to block and even repel oncoming attacks, very useful for a ranged type attacker. Even if Kakyoin's emeralds can break through the barrier because of Stand properties the Emeralds are only large building level, the Guyver, is well above that, as it can fight with city level Zoanoids and having a base durability 20 times stronger than steel.
Being able to take out multiple superior hyper Zoanoids with ease and tanking all their attacks as well, keep in mind that Kakyoin will also have to destroy the control medal if he wishes to kill the Guyver assuming he can get past his defenses.
And with access to gigantic form Guyver's megasmasher should be able to get past Zebra's durability as well