I have followed the link below to simulate two different zero-padding methods (zero-centered and casual)

https://ccrma.stanford.edu/~jos/mdft/Zero_Padding.html

Sample code

close all;
clear all;

x           = [3 2 1 1 2];
n           = length(x);

fft_len     = 64;

zeropadd    = fft_len - n;

y           = [x(1:(n-1)/2+1) zeros(1,zeropadd) x((n-1)/2+2:end)];

x_zeropad   = [x zeros(1,zeropadd)];

y_fft       = fft(y);

x_fft       = fft(x, fft_len);

x_zp_fft    = fft(x_zeropad);

subplot(311)
stem(y_fft)
xlabel 'n',
ylabel 'fft(y)'

subplot(312)
stem(x_fft)
xlabel 'n',
ylabel 'fft(x)'

subplot(313)
stem(x_zp_fft)
xlabel 'n',
ylabel 'fft(x_zp)'

Output is

My question is why is the spectrum of fft(y) is different from fft(x) and fft(x_zp)