Don’t start and stop a task, stick with it until it’s knocked out. When you jump back and forth between tasks you’re not multitasking, you’re slowing down progress. It should be your goal to only have to touch a single task in a project one time, not half now half later. When splitting up tasks, it takes time to get back up to date with what you were doing in the first place.
Assess what you need to do and do it. If you get a call, an email, or a request in any other form, write that down and come back to deal with it at a better time.