Catalan forward Olmo spent six years in the youth ranks at Barca's famed La Masia before making the surprise switch to Croatia in 2014.
The 21-year-old was named man of the match after he scored the winner in Spain Under-21s' European Championship final victory over Germany in 2019.
He brought that form into this season with a string of impressive displays during Dinamo's Champions League campaign, earning a first senior Spain cap in November – another occasion Olmo marked with a goal against Malta
Dinamo reportedly want €40million for Olmo, who hopes to arrive at Camp Nou in January rather than the end of the season if an agreement is reached.
"It makes me happy the rumours have become a formal proposal and Barca are planning my return," Olmo told L'Esportiu. "I spent six years at La Masia and they taught me values for a lifetime.
"I do not know if Barca wants me now or at the end of the season, it's something my representatives control.
"If there is an agreement between the clubs, it seems to me it is best to leave Zagreb now."
Olmo believes joining Barca in January would aid his development and boost his chances of securing a spot in Luis Enrique's Spain squad for Euro 2020.
"My goal is to go to the European Championship and it will be difficult for me in the next few months if I only play in a minor competition," he said.
"Not only for going to the European Championship, also for continuing to improve. I am prepared to take a step forward in my career."