"HYDRA had tech that was far advanced for our time." He was sure that Tony would know about that a little bit at least, it was probably in the SHIELD files and Howard probably talked about it a bit. Stark knew about all things technology, well most at least, and he was able to talk with Dr. Banner about all that biology stuff.

And Dr. Erskine's formula for him still hadn't been replicated fully.

Bucky's reaction confirmed his guess about HYDRA though. It made him sick that they got their hands on his friend again, but this time, he wasn't there to rescue him. Come to think of it... he probably survived the fall due to whatever Zola did to him. But HYDRA was supposed to be gone now, right?

"Is... HYDRA still using you? Even in the present?"