A very long Terza Rima
JavaScript (ES6), 51 50 49 bytes
Saved 1 byte thanks to @l4m2
f=(n=45358)=&gt;n%63?f(n-1333)+n.toString(36)+' ':''

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How?
We start with n = 45358 (yzy in base-36). We subtract 1333 from n at each iteration (111 in base-36). We stop as soon as n MOD 63 = 0, because 12033 (9a9 in base-36) is the first value for which this condition is fulfilled, and 63 is the smallest modulo with such a property.
Decimal | Base-36 | MOD 63
--------+---------+-------
  45358 |   yzy   |   61
  44025 |   xyx   |   51
  42692 |   wxw   |   41
  41359 |   vwv   |   31
  40026 |   uvu   |   21
  38693 |   tut   |   11
  37360 |   sts   |    1
  36027 |   rsr   |   54
  34694 |   qrq   |   44
  33361 |   pqp   |   34
  32028 |   opo   |   24
  30695 |   non   |   14
  29362 |   mnm   |    4
  28029 |   lml   |   57
  26696 |   klk   |   47
  25363 |   jkj   |   37
  24030 |   iji   |   27
  22697 |   hih   |   17
  21364 |   ghg   |    7
  20031 |   fgf   |   60
  18698 |   efe   |   50
  17365 |   ded   |   40
  16032 |   cdc   |   30
  14699 |   bcb   |   20
  13366 |   aba   |   10
  12033 |   9a9   |    0