This results from the process of encoding and decoding audio and is unavoidable. Due to physics and distance, absolute zero latency is impossible, but there are two main ways to minimize lip sync issues:
(1) Use an aptX or aptX-LL Bluetooth device to play audio. Note BenQ projectors only support the SBC (Sub-Band Codec) audio coding format.
(2) Instead of Bluetooth, consider using wired speakers or headphones.