It should be noted, firstly, that the concept of Emptiness (shunyata) does not exist in the Theravada tradition of Buddhism. It is a Mahayana Buddhist term. The term closest to Emptiness in Theravada Buddhism is Non-self (anatman). So why these separate terms?
In Theravada Buddhism the Buddha’s teaching of Non-self is interpreted to mean only no essence of the self, the sentient being. Mahayana Buddhism interprets Non-self to mean all things, animate as well as inanimate. This is why Mahayana Buddhists to distance themselves from the term No-self by taking a word to cover the wider definition they believed the teaching of Non-self to mean.
This is why Form and Emptiness are spoken within the same breath in the Heart Sutra. Whether one accepts the Theravada or Mahayana is up to the individual. What is important is to know at least this difference exists in Buddhism. It is a matter of interpretation.
I started out in Buddhism with Zen Buddhism. I think it has a lot to offer. But at the same time one should think about what it doesn’t offer. One should weigh the pros and cons.
One of the interesting developments in Mahayana Buddhism (of which Zen is a part of) is that of the Bodhisattva and its (it is both a he and she. And it is a non-existent person) ideal. A bodhisattva is said to strive to save all beings before its leaves this world into Nirvana, the final extinction.
In contrast the Theravada has the Arhat ideal. An Arhat is anyone who has vowed to become enlightened, the highest ideal that leads to contentment. Mahayana sees the Arhat ideal as selfish which is why they developed the Bodhisattva ideal. This was a later development after the Buddha’s time.
So if you ask me which is “correct” I will say both.
I doubt The Buddha meant for his teaching to be selfish (the supposed Arhat ideal interpretation) in any way. But neither did he mean for it to be an active and engaging teaching (the Bodhisattava interpretation) either.