First of all this is a solid first Kaizo hack imo, there is actually not that much to criticize.
Well, most parts of the level are really easy and there is nothing wrong with that, but some parts are a bit too
For example you can just stomp the Clappin' Chuck in screen 02 and that's not challenging at all. There are many ways to make this part more challenging without making it too hard. You could simply remove the cement block and the Clappin' Chuck for example or you could come up with a bit more clever setup where you need the Chargin' Chuck to cross the gap.
Another example is the Yoshi jump. The jump is way too easy, while something like this for example:
would make the jump a bit more difficult.
But I like the part after the Yoshi jump. I'm not sure if I did it right though, but I think you have to trigger the invisible coin block first, then throw the shell against the coin block, land on the shell in mid-air and then land on it again when it comes back to stop the shell. (or is there an easier solution?) This part is more difficult than the rest of the level, but it's fun and not too hard either.
I don't mind floating Munchers that much, but the few floating Munchers in screen 0D aren't beautiful either. In this case you can simply put ledges underneath them without making the part easier.
There are some other things in the level that don't look that good (for example the Munchers in screen 07 are floating 1 pixel above the ground due to the pipe underneath them), but these are only minor things.
Breaks in the Level:
A minor break first
- in screen 0D you can jump from the note block on top of the small horizontal pipe. (or on the big pipe first and then on the small one)
And now a bigger break
-in the little underground section you can take the shell before the Kooper kicks it, by scrolling the screen to the left and then you can easily finish the level while holding the shell and therefore finish the level as big Mario. That's not a big problem in a one-level hack, but if you decide to add more levels to your hack, something like this could be a crucial break.
So yeah, that's pretty much everything I noticed while playing the level, I hope this feedback helps a bit.