いちど一度ichidoni
1.

A situation in which multiple events or actions occur simultaneously, or when a single task is accomplished in one instance, rather than incrementally.

2.

The occurrence of several distinct items or actions happening together as a unified event or in a single effort.

3.

The simultaneous execution of various actions or the gathering of multiple things in a single moment.

Example:

一度にひとつのことをするようにしなさい。