"Grabbed some zs" is a casual way of saying that you have gone to sleep or taken a nap. There are a number of other colloquial expressions that can be used to convey the same meaning, such as "hit the sack," "hit the hay," and "hit the pillow." Other possible synonyms include "dozed off," "nodded off," "snoozed," "drifted off," and "caught some shut-eye." No matter which of these expressions you use, they all convey the same basic message: that you have taken a moment to rest, relax, and recharge your batteries before getting back to your daily routine.