If you've shaved the fur off a Shih Tzu it can take from 6 to 8 weeks to start seeing the Shih Tzus fur or hair to grow back.
It can then take a full one year before the Shih Tzu has it's hair fully grown back after shaving or cutting it.
While it's growing out be sure to comb it to help prevent the Shih Tzu's hair from getting tangled.