Lands you control can tap to produce at least ({4} magic symbol) ({R} magic symbol) ({G} magic symbol) ({W} magic symbol) .
({2} magic symbol) plus enough mana to pay for commander tax, if applicable available.
Steps
Activate all mana-producing lands you control by tapping them, adding at least ({4} magic symbol) ({R} magic symbol) ({G} magic symbol) ({W} magic symbol) .
Cast Zacama either from your hand or from the command zone by paying ({6} magic symbol) ({R} magic symbol) ({G} magic symbol) ({W} magic symbol) plus commander tax, if applicable.
When Zacama enters the battlefield, it triggers twice.
Resolve the first trigger, untapping all lands you control.
Activate all mana-producing lands you control by tapping them, adding at least ({4} magic symbol) ({R} magic symbol) ({G} magic symbol) ({W} magic symbol) .
Resolve the second Zacama trigger, untapping all lands you control.
When Shivan Wurm enters the battlefield, it triggers twice, returning itself and Zacama from the battlefield to your hand.
Repeat.
If lands you control can tap to produce at least ({5} magic symbol) ({R} magic symbol) ({G} magic symbol) ({W} magic symbol) , this combo nets infinite mana, and you may use that mana to activate Zacama's other abilities.