Try connecting your phone to a PC via a USB cable, then select the option to connect your phone as a media device (MTP). (Pull down the notification bar on the home screen to select your USB options when you are connected to a PC)
Your phone will now show up in Windows Explorer under Computer as ZTE ZMax (I think). Expand this 'drive' to show sub folders of phone storage and SD card. Expand the folders to find the folder where your pictures are, copy them to your computer and then delete them from your phone or simply cut and paste.
Be careful not to delete anything else. It might be important!
If the pictures are on the SD Card in the phone, and you have a card reader connected to your PC, simply unmount the card from the phone (or with the phone switched off simply remove it) insert it in the card reader and then copy the pictures to your PC and then delete from the card.
If you connect your phone to a PC via a USB cable and select MTP option in the phone as above, then using Windows Explorer, scroll to ZTE ZMax > Phone Storage > DCIM > Camera can you see your pictures there. Here is an image of where the pictures are in my ZTE T815 so hopefully yours will show up there as well.
Apologies if you have already looked here.