Here's some comparative specs.

Pana X 12-35 f2.8 II

- Lens construction = 14 elements in 9 groups
- Closest focusing distance = 0.25m / 9.84 in.
- Maximum image magnification = 0.17x

(0.34x : 35mm equivalent)
- Filter size = 58mm
- Dimensions = φ67.6 x 73.8mm / φ2.66 x 2.91 in.
- Weight = Approx. 305g / 10.8 oz.

Olympus 12-40 f2.8 Pro

- Lens construction = 14 elements in 9 groups
- Closest focusing distance = 0.2m / 7.87 in.
- Maximum image magnification = 0.3x (0.6x : 35mm equivalent)
- Filter size = 62mm
- Dimensions = φ69.9 x 84.0mm / φ2.75 x 3.31 in.
- Weight = 382g / 13.5 oz.

Olympus 12-100 f4 Pro

- Lens construction = 17 elements in 11 groups
- Closest focusing distance = 0.15m (Wide) / 0.45m (Tele)
- Maximum image magnification = 0.3x (Wide) / 0.21x (Tele) (35mm equivalent: 0.6x (Wide) / 0.42x (Tele))
- Filter size = φ72mm
- Dimensions = φ77.5 x 116.50mm
- Weight = 561g / 19.8 oz.

Panasonic Leica 12-60 f2.8-4

- Lens construction = 14 elements in 12 groups
- Closest focusing distance = 0.20m / 7.87 in.
- Maximum image magnification = 0.3x (0.6x : 35mm camera equivalent)
- Filter size = 62mm
- Dimensions = φ68.4 x 86mm / φ2.69 x 3.39 in.
- Weight = Approx. 320g / 11.3 oz.

Olympus 12-45 f4 Pro

Closest focusing distance: 12 cm at 12mm, 23 cm at 45 mm

Max image magnification: 0.25x

Filter Size: 58mm

Dimensions: 63.4x70mm (2.5" dia x 2.76" long)

Weight: 254 g (9 oz)

So, 12-45 Pro is smaller than all those other lenses. Hopefully, less expensive too!