Saying Zoro is comparable to G5 in speed is classic side by side scaling clown show lmao.
Sanji fans shouldn't complain though, cause they do it all the time.
Serious answer:
Zoro has better attack speed/CQC, Sanji has better movement speed. Luffy is good in both. Should be obvious
Zoro's movement speed isn't "slow" by any means, but it is, when relatively measured to Luffy and Sanji