There's very minimal differences in terms of graphic performance between the two (as both GPUs being compared are both GTX 1070s). What sets them apart are their power consumption, noise, heat dissipation, size, warranty, LED lighting, and branding - such for the price difference.
Both have the same base clock-boost clock speeds, video output ports, number of fans (dual), backplates, and BIOS chip.
The Zotac requires 2x 8-pin PCIE connectors while the Msi requires 1x 6-pin + 1x 8-pin. The Zotac has RGB lighting, while the Msi has Red Lighting. The Zotac is longer at 300mm while the Msi is only 279mm. Zotac offers 5 year warranty while Msi offers 3.
If none of those differences matter to you, get the cheaper Zotac.