Can you take Tylenol and Zyrtec?

Yes, if it is just plain Tylenol with just plain Zyrtec, then there are no serious interactions.

If it is a Tylenol cold formula, then you need to read the box.

Most of the Tylenol cold products have some combination of antitussive, decongestant, antihistamine and acetaminophen. Please check your container for the ingredients. If there is an antihistamine (usually chlorpheniramine or diphenhydramine), then do not take the Zyrtec (cetirizine) which is an antihistamine.