Go to sleep and Zonk out

Go to sleep verb - Prepare for sleep.

Zonk out and go to sleep are semantically related. In some cases you can use "Zonk out" instead a verb phrase "Go to sleep".

Zonk out verb - Fall asleep fast, as when one is extremely tired.

Go to sleep and zonk out are semantically related. Sometimes you can use "Go to sleep" instead a verb "Zonk out".