These cancel out. Q sub zx and Q sub xz, these two also cancel out.

这些也相互抵消了，Qzx和Qxz也抵消了。

youdao

These cancel out. Q sub zx and Q sub xz, these two also cancel out.

这些也相互抵消了，Qzx和Qxz也抵消了。

youdao