Not a huge historical area but was the place the first Spanish ship headed out to the Philippines.
Troncones is basically a small village over run with gringos who now own most of the beach front homes.
Lovely beach but very rough surf/riptide. Nice to watch but made for surfers.
Petatlan is a nice day trip with one of Mexico's few gold markets. Gold tallers with ready made items or to your design. Also unique white church with a black Jesus said to preform miracles.
Barra de Potosi is a real gem. 91/2 mile lovely mostly empty beach, great beach cafés, a lagoon ideal for kayaking which rent for 100 pesos per hour. A number of nice Inns & small hotels.
Zihuatanejo has excelcelent cafés with low prices including MCafé Cafe, Paapa Loca's. several in Pozole ally, Salvador's Daniel's, & Csa Vieja to name just a few. 4 beaches all swimable with La Ropa the longest & most popular. Others are Playa Madera, Las Gatas & Municipal.
A nice museum, the normal boat tours, great fishing & good shopping.

PS The above mentioned Lagoo is ideal for birding. Also near by is the Refugio de Potosi a most interesting place. Crocadillo preserves, a great hiking/biking trail in Ixtapa & of course lots of beach walking.