If it's large enough for say 2x or more "retina" usage... a very minor soften filter, then color reduction to get well under 256 colors (often can do 32-64) quantization and oxipng w/ zopfli can go a long way... just getting down to a palette over rgb for png brings down sizes a lot... palette reduction to around 32 colors does a bit too. Just depends on the material.
That said, the actual size of this image is massive compared to where it needs to be, and looking at it, should definitely be able to quantize down to 32-64 colors and reduce the size to even 4x the render size... let alone just using svg, as others have mentioned.
That said, the actual size of this image is massive compared to where it needs to be, and looking at it, should definitely be able to quantize down to 32-64 colors and reduce the size to even 4x the render size... let alone just using svg, as others have mentioned.