וַיֹּ֨אמֶר הַמֶּ֜לֶךְ לָהֶ֗ם קְח֤וּ עִמָּכֶם֙ אֶת־עַבְדֵ֣י אֲדֹנֵיכֶ֔ם וְהִרְכַּבְתֶּם֙ אֶת־שְׁלֹמֹ֣ה בְנִ֔י עַל־הַפִּרְדָּ֖ה אֲשֶׁר־לִ֑י וְהוֹרַדְתֶּ֥ם אֹת֖וֹ אֶל־גִּחֽוֹן׃
And the king said unto them: ‘Take with you the servants of your lord, and cause Solomon my son to ride upon mine own mule, and bring him down to Gihon.
Mesilat Yesharim
The means through which Zeal is acquired are the same ones through which Watchfulness is acquired, and their levels are likewise similar as I wrote earlier.