In short, no. You can ask, and they have the option to accept or decline.
Any change to your employees terms of employment needs to be agreed between both parties, and after a fair consultation process. The duration of that process needs to allow time for feedback and consideration by the employee BUT doesn’t have to take weeks, particularly in light of the economic pressures for a small business right now.
I would recommend applying for the economic subsidy (if you haven’t already) via https://workandincome.govt.nz/products/a-z-benefits/covid-19-support.html#null in the first instance, as it has been set up to support keeping employees in paid employment.
If you don’t believe you can sustain their employment even with the subsidy, then it would be best to move quickly into a consultation process to advise a stand-down unpaid leave or termination of employment as options.
Some companies have done this and employees have come back offering temporary reduction in salaries, or taking LWOP. While they’re on LWOP with you, they can work for other organisations such as MOH Healthline, supply chain carriers, Supermarkets which is desperately seeking headcount, then return to you.
Happy to assist in more detail if you need.