How to allow object to have optional fields but one must be selected

[cill-i-am]

I have two checkboxes in a form, either can be optional but one must be selected to proceed. I'm not sure how to make it work though. My original schema is below

options: z.object({
        health: z.optional(z
            .string({ required_error: 'A health package is required' })
            .min(1, 'A health package is required')
            .transform(val => val === 'on')),
        retirement: z.optional(
            z
                .string()
                .min(1, 'A retirement package is required')
                .transform(val => val === 'on'),
        ),
    }),

I have also tried this, nut with no success

options: z.union([
        z.object({
            health: z.string({ required_error: 'A health package is required' })
                .min(1, 'A health package is required')
                .transform(val => val === 'on'),
            retirement: z.string({ required_error: 'A retirement package is required' })
                .min(1, 'A retirement package is required')
                .transform(val => val === 'on'),
        }).strict(), // .strict is needed for your use case to work properly
        z.object({
            health: z.string({ required_error: 'A health package is required' })
                .min(1, 'A health package is required')
                .transform(val => val === 'on'),
        }).strict(), // .strict is needed for your use case to work properly
        z.object({
            retirement: z.string({ required_error: 'A retirement package is required' })
                .min(1, 'A retirement package is required')
                .transform(val => val === 'on'),
        }).strict(), // .strict is needed for your use case to work properly
    ]),