tú Díselo

tell it to him, tell it to her

→ decir
dí to say, to tell + se 3rd-person indirect object pronoun + lo him/it object pronoun
verb · 2nd-person singular informal Rare #52,879
tell it to him, tell it to her A command addressed to one person informally.
SP: Díselo a Marta ahora.
EN: Tell it to Marta now.
Conjugation of decir

¡Díselo a él, no a mí!

Tell him, not me!

¡Díselo!

Tell them!

— Asuntos infernales (2002)

¡Díselo a la policía!

Tell the police!

— La Tumba de las Luciérnagas (1988)

¡Díselo a él!

Tell him!

— Такси-блюз (1990)