Sylvia Park manager Jonathan Douglas said due to the expectation of big crowds on Saturday, the mall will open at 7am "to allow shoppers to prepare for the opening of H&M at 10am."
It will remain open until 7pm on Saturday, and will be open until 9pm next Thursday, after Zara opens that morning.
Shoppers are warned to expect queues at both stores - which management says are likely to form before the doors open.
Last year, at the opening of H&M Cape Town, keen shoppers queued outside the store 24 hours before opening. And in November, hordes of keen shoppers queued outside Zara's first Brisbane store.
Zara is the world's largest fashion retailer, and is owned by Spanish billionaire Amancio Ortega, Europe's richest man, according to Forbes.
The brand was established in 1975, and parent company Inditex also owns brands Pull&Bear, Massimo Dutti and Bershka.
Zara is known for translating high fashion catwalk designs to their high street stores in record time.
In July, the company was accused of copying the work of artist Tuesday Bassen.
Swedish company Hennes & Mauritz (H&M Group) has stores in 62 countries worldwide, and online shopping in 32 countries.
Alongside H&M, the retailer owns brands including COS and Cheap Monday.
In 2015, the group reported a profit of $34 billion, and opened 413 new stores - including H&M outlets in Taipei, Peru, Macau and New Delhi.
It is the world's second biggest clothing retailer, after Zara's parent company Inditex.
Both Zara and H&M achieved a high score in the 2016 Baptist World Aid ethical fashion guide - which grades companies based on their labour rights management systems.