Yes, ZEALOT is a Scrabble word!

Letter values in Scrabble US: Z 10, E 1, A 1, L 1, O 1, T 1.

Is it a valid word?

ZEALOT is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a member of an ancient Jewish sect in Judea in the first century who fought to the death against the Romans and who killed or persecuted Jews who collaborated with the Romans
a fervent and even militant proponent of something