Check out the Sonance line of outdoor speakers. They have a wide range of products for outdoor. Their Mariner line of mounted speakers are outstanding. They also have a variety of rock speakers, "satellite" speakers (that look like landscape lights), in ground and above ground subwoofers, and amplifiers.
Depending on how sophisticated/expensive you want to go:
A Control4 system would be something to consider, especially if you wanted to do any video or home automation as well. Their controllers have local streaming from Tidal, Spotify, Pandor, XM, and a few others and can control both audio and video zones. Their multi-zone amps are very good. I have an all C4 system with 4 outdoor audio zones (with Sonance Mariners), 4 indoor audio zones, and 8 video zones and it is a very slick system, all operated via wifi through the C4 app.
You could use something like a Sonos Connect or Bluesound Node which would also stream locally via wifi and connect to any multi-zone amp. I had a Niles multi-zone amp in my old house which I thought was great. Dayton Audio makes a very affordable multi-zone amp which a friend of mine has in his wine store hooked up to several zones of JBL mounted speakers (with and SVS sub) and the sound is really quite good.
My A-V guy does all of this kind of stuff and has several branches here in KY. PM me if you want his contact info.
