If the speakers are there and all of the wires are run then you could likely get away with a small zone amplifier for those 4-5 zones.

Something like this https://www.amazon.com/Wireless-Bluetooth-Power-Amplifier-System/dp/B08ZR8W8JK/ref=mp_s_a_1_3?crid=13XABG2GY7EMW&keywords=5+zone+amplifier&qid=1684899590&sprefix=5+zone+amplifier%2Caps%2C236&sr=8-3