It seems that something went wrong when preparing first partition with BOOT.BIN and image.ub files.
First method : A minimal test that we can do is to prepare only one FAT32 partition and copy BOOT.BIN and image.ub files. Then start the board with this setup. This way it should only start the Linux kernel, however no rootfs. The UART should be initialize. and the green LED should be on.
Step 1: format SD card as FAT32 file system
Step 2: copy BOOT.BIN and image.ub files to the SD card (then safety remove the SD card)
Step 3: insert SD card in zybo-z7-20 and power the board
Step 4: The green LED turns on then it means that the UART(via FTDI) is ready.
Alternative: The second file attached was z7-20.img.zip which is a snapshot off a 2GB SD card containing both partitions. The image can be written to the micro SD card with `dd` tool on Linux or a similar tool for Windows (writing this image to SD card from windows 10 worked for me using Win32DiskImager).
Step 1: extract the z7-20.img.zip
Step 1.A : insert micro SD card if not already inserted.
Step 2: run Win32DiskImager
Step 3: For `Image File` field set the path to z7-20.img file.
z7-20.img sha1sum: e08516edb24ff65d32ce7a43a946f0be9b9f0ebe (If you want to check)
Step 4: In `Device` field make sure the Drive letter for microSD is selected (If not you risk loosing data from other devices).
Step 5: Pres write.(If you are prompted to format partitions please do not. The second partition filesystem is ext4 which is not recognized by the OS)
Step 6: After the process ended, safety remove the micro SD.
Step 7: Plug the micro SD into the z7-20 board. Power up the board.