Question

If you breed a ditto (shiny) and any other Pokemon (shiny) is it a (shiny)?

Answer 1

There is a chance that it would be shiny but its not guaranteed. There is no current legal way to guarantee yourself a shiny Pokemon from a egg.

Comments

Unless you use RNG Manipulation

Answer 2

There is no increased chance to breed a shiny Pokemon by either of the parents being shiny. The Shininess of a Pokemon is determined separate from the parent's shininess.

One way to increase the chances of a shiny is by using Matsuda method, which is to have two Pokemon breed together from different language games (e.g. Japanese Ditto + English Eevee).