The Vernier Sensor Block for MINDSTORMS EV3 software does not have a Zero function. You can easily create a correction in your program to effectively zero the sensor reading:
1. Determine what the sensor is reading when it should read zero. This is the offset value.
2. Insert a Math block to correct the value by that amount.
3. Select the subtraction setting on the Math block and enter the offset value into the b box in the Math block.
4. Wire the Numerical Value of the sensor reading into the a box.