Yes — a telescope can be used as a very long fixed-focal-length lens for terrestrial photography. It is not a zoom; focal length is fixed, and changing magnification normally involves different eyepieces, not zooming.

Focusing is usually possible for distant earthbound subjects, and users report telescopes can focus much closer than astronomical infinity. They can work well for relatively static subjects like birds at long range.

Practical tradeoffs:

• Most setups are manual focus only, and at long focal lengths depth of focus is very thin.
• Some telescope types are awkward for daytime use; refractors, SCTs, and Maks are generally more practical than Newtonian reflectors.
• Many telescopes have a curved focal plane, so edge sharpness may suffer on camera sensors unless you use a field flattener or a scope designed for imaging.
• A solid mount is important; with a balanced mount, panning can be smooth.

So the idea is viable, especially for specialized long-reach work, but it is less convenient than a purpose-built telephoto lens because of manual operation, mounting needs, and possible optical compromises.