If it is a true-rms ac multimeter, such as the 170 series, 80 series or 280 series it will not zero and should not be zeroed. Most of these true-rms type multimeters have a minimum ac voltage and current level specification for both the ac volts and ac current modes, typically specified from 3% to 5% of range. When a signal is applied above the specified minimum level, the meter will meet its accuracy specifications. You will find this specification in the specification section in the rear of the user manual.
Example from the 80 Series V user's manual (page 44):