0.25 W Zener — what the rating tells you
The HZS3CLLRX-E is a 0.25 W Zener diode, a general-purpose voltage-reference or clamping device for low-power rails on control boards, sensor interfaces, and auxiliary supplies. The 0.25 W dissipation ceiling means the diode can handle about 250 mW of continuous power at 25 °C ambient — enough for a 5.1 V shunt regulating a few milliamps, but not for a main power rail.
ROHS3 compliance is confirmed, making it suitable for EU and other RoHS-regulated BOMs without a waiver.