Colossal Eren can harden his fists and still use Annie fighting style (even in this form) that he had learned (we see it when he fights Colossal Armin. He still raises his fists like Annie).
Seeing how he destroyed Colossal Armin, he should be able to defeat his version with WHT. Especially since WHT Eren doesn't use his power like Lara Tybur, he doesn't crystallize. Eren is still in the nape.
WHT Eren will end up crushed, swept away. His attacks will not do anything to Colossal Eren (especially if he can use hardening too). It will be almost like Eren vs Berthold in Shiganshina. Bert destroyed Eren and send him fly.
Moreover, to defeat Colossal Eren you must not attack the nape but destroy Eren's head inside the mouth (at 50 meters high). I don't know if WHT know this ability (perhaps since he saw future).
Besides (pure speculation) maybe it won't be enough to kill Eren (but we'll see that when 139 will come
It's going to be a no match if Colossal Eren can shoot heat out of his body like Berthold but since he didn't used that against Mikasa and Levi, I'm going to say he can't do it.
Colossal Eren low diff.
Colossal Titan is really on a whole other level (if you exclude the Founding Titan).