This used to be a great service
That all stopped when they terminated their own delivery service and entered a "partnership" Caviar and DoorDash in order to make their program more widely accessible. DeliverZero's website and app were effectively disabled, forcing users to go through the mainstream apps to order. They now charge a fee to order with the reusable containers and you can no longer drop them off with the delivery driver. It's not inconvenient, but every bit of friction they add to the process disincentivizes consumers from using this more environmentally option.
On top of it all, I can't in good conscience give my money to the mainstream delivery apps that have consistently opposed NYC laws that would have given delivery drivers a living wage. Instead, delivery workers are forced to break traffic laws and ride on sidewalks in order to maximize the number of deliveries. It is with regret that I can no longer support this app.