People from all over Shropshire and beyond are holding events and collecting funds for Zac, who has an extremely rare form of childhood leukaemia called Near Haploid, and needs to travel to the US for specialist treatment unavailable on the NHS.
Zac's family has collected more than £288,000 of the £500,000 needed for the treatment – and it shows no signs of slowing down.
Mark Garbett, Zac's father, said it was amazing to see how far the cause has spread.
"I think it's almost bigger than we think it is," he said.
"It's absolutely incredible to see how far it has reached and that it is now among the inner circles of celebrities.
"We've now had donations from all over the world, from places as far as Saudi Arabia and Australia.
"It's very heart-warming to know Zac is in the mind of so many people and it's touched us to see people such as Jonathan Ross and Stiliyan Petrov find out about Zac and donate."
There will be a Wear Red for Zac fashion show on Sunday at Telford's International Centre, starting at 7pm.
It will be the perfect end to a Zac-focussed day, with hundreds of people gathering in Telford Town Park for Zacfest.
As well as live music and activities, the festival will be the site of a record-breaking attempt with a difference. The crowd will try to become the most people to sing Baby Shark at once.
How you can help:
- Anyone who wants to support the fundraising campaign should visit justgiving.com/crowdfunding/zac-oliver
- Anyone donating is asked to make sure they post a picture of themselves wearing red on September 28 on Facebook or Twitter with the hastag #wearredforzac
- People can also join Zac's Facebook support page which is called 'Zachariah's's fight against Acute Lymphoblastic Leukaemia'.
- People can also donate using their mobile phone by texting ZACH75 £1 to 70070.
Money is still flooding in for the cause, with businesses raising thousands of pounds.
Syspal, in Broseley, has donated £2,000, with employees raising £570 from a cake sale.
JBS Kickboxing held a kickathon to help raise funds for Zac and collected £1,000.
More Zac news:
- TV star Jonathan Ross boosts fund - and youngster gets a gritter named after him
- Baby Shark adds bite to Zacfest
- Shropshire Star comment: Zac’s the spirit you lovely lot
Bridgnorth Running Club held its own Wear Red For Zac event, with more than 40 people getting involved, raising more than £250.
Club member Nina Williams said: "There was a fantastic turn out from the running club and I want to thank everyone who came and donated.
"We raised £251.67 and there is still a bit more to come in from members who couldn’t make it and we will combine this with the £110 which club member Dana Power raised when he completed a walk up the steps of Bridgnorth dressed as Puff the Dragon.”