Zero-pad before or after windowing for FFT
If done correctly, the order should not matter. You apply windowing to remove the jumps at the end of the signal segment by fading the values there to zero. Zero-padding then continues with zeros. Irregardless if padded or not, the windowing should only be applied to the original signal segment.

The wrong way would be to zero-pad and then apply windowing to the now longer signal over its full length, i.e., without regard to the position of the jumps. This would not remove the jumps and thus keep the background in the spectrum that is not related to the frequency content of the signal but the segmentation method.