Multitasking is a myth. Even though humans can perform multiple tasks at once, we’re not particularly good at it.
Computers, on the other hand, are built for multitasking and subsequently excel at doing so. In computing terms, tasks are sometimes referred to as threads. A computer’s processor isn’t influenced by hormones or lack of sleep and is typically built to run as many threads as possible at the same time.
For us people, with 100% of concentration (and dedication) to divide over tasks, running four tasks (simultaneously) results in 25% focus per task. Suppose they are easy, repetitive tasks that don’t necessarily require a lot of creativity or intelligence. In that case, you might get away with it. If that’s not the case, consider changing your workflow from parallel to sequential.
Pick up tasks that require full focus, one at a time, back to back.