I have a 55-210 zoom lens, and the specs show that the minimum focus distance is 1m. Does that distance remain constant if I use the zoom? Or does that change it? Thanks in advance!
It ultimately depends on the design of the specific lens model (which you have not provided). Most, but far from all, telephoto zoom lenses have roughly the same MFD over their entire focal length range. But there are plenty of exceptions.
Most folks are concerned with MFD primarily with regards to how it affects maximum magnification. For the vast majority of zoom lenses, MM and MFD are both found at the longest focal length, so that's all most lens makers tend to publish in their specs.