${\theta }_1\left(2z,q\right)=2\frac{{\theta }_1\left(z,q\right){\theta }_2\left(z,q\right){\theta }_3\left(z,q\right){\theta }_4\left(z,q\right)}{{\theta }_2\left(0,q\right){\theta }_3\left(0,q\right){\theta }_4\left(0,q\right)}$