Deleting a Mac Partition on a drive that has bootcamp?
From within OSX you should be able to delete both the empty mac partitions, then create a new one, all using Disk Utility.

Here's a good guide: https://www.lifewire.com/resize-mac-disk-utility-volume-os-x-el-capital-later-3573395

Given that both partitions are empty there's no risk of data loss here. Just wipe them both out and create one large one.