Napoli midfielder Zielinski has thrived for the Partenopei since joining from Empoli in 2016.
Only forwards Jose Callejon (63) and Lorenzo Insigne (86) created more chances in Serie A last season for the club than Zielinski (53), while he completed more passes than any team-mate except for Fabian Ruiz and Giovanni Di Lorenzo.
Toni Kroos (60) was the only midfielder for Barca or Madrid in 2019-20 who created more goalscoring opportunities than the Poland international.
Reina, a team-mate of Zielinski for two years in Naples, has no doubt the player is good enough for one Spain's biggest two clubs.
"I have a crush on Zielinski!" he told Cadena SER. "He's a Real Madrid or Barcelona player. He is out of the ordinary."
Reina, who was on loan at Aston Villa from Milan last season, is now with Lazio as he continues a senior career in football spanning 20 years.
The 38-year-old thinks Manchester United's David de Gea is presently the best option for Luis Enrique's Spain side, but he believes there is an unfair prejudice towards older players compared to the attitude in Italy.
"The one with the most playing consistency is De Gea and it has to be that way, for me," Reina said.
"Luis Enrique has a choice of young goalkeepers or more expert, 38-year-old goalkeepers.
"David has experience that will for sure make him the most prepared. Kepa [Arrizabalaga] is going through a worse time due to the signing of Mendy. There's also [Sergio] Asenjo, [Fernando] Pacheco... there are a lot of names.
"The culture in Spain is that a 38-year-old player is seen as much older than he is in Italy. Here, respect is different. In Spain, they see you as an older player."