Also the timing gets throw off a little bit if you only do 3C. if you add something in front it helps make it feel more like how the combo will cause if you try and practice with just 3C > 214D~66B > 5A it will be a little more odd.
if you struggle with 3C > 214D~66B
You must first practice 3C >214D~66. you should try and make the 66 come out as quickly as possible. i try and do it all in one fluid motion so I go 3B214. pretty much start at 3 roll to 4. that makes the stance come out as fast as possible. Usually the problem with the ~66B part is making sure you do 66 as quick as the game will let you. this means you need to make sure you have the timing where if you input 66 it will come out not too late. easy way to figure that out is do the 3B214 and input 66 really fast. it shouldn't come out if you do it too fast so start too fast. and slow down till you get it to come out perfectly. Once you get that timing down when you actually use the 66B you can not delay the animation for the kick. the B follup must be right after 66 to the point where you might not even really notice the dash. Once you get that timing down connecting 5A is easy.
... 3C > 214D~66B > 5A takes a lot of practice. At least it did for me. if you are still struggling after putting in a lot of labwork let us know and see if we can help further. I'm a hazama scrub who just got the motion down this week and i still don't have it perfect yet.
Also. hazama trial #17 It shows you. forces you to do it. and you can slomo it and hear/see how fast they input it.